Golf ball covers made from plasticized thermoplastic materials

ABSTRACT

Multi-layered golf balls containing a two or three-layered cover assembly are provided. In one embodiment, the cover assembly includes a relatively hard inner cover and relatively soft outer cover. Alternatively, the cover assembly may include a relatively soft inner cover with a relatively hard outer cover. Three-layered covers comprising an inner cover, intermediate cover, and outer cover layer also may be prepared. Preferably, at least one of the layers is formed from a thermoplastic composition that preferably comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-assigned, U.S. patentapplication Ser. No. 14/460,416 filed Aug. 15, 2014, which is acontinuation-in-part of co-assigned, U.S. patent application Ser. No.14/145,578 filed Dec. 31, 2013, which is a continuation-in-part of U.S.patent application Ser. No. 13/323,128, filed Dec. 12, 2011, now U.S.Pat. No. 8,715,112, which is a divisional of U.S. patent applicationSer. No. 12/423,921, filed Apr. 15, 2009, now U.S. Pat. No. 8,075,423.U.S. patent application Ser. No. 12/423,921 is a continuation-in-part ofU.S. patent application Ser. No. 12/407,856, filed Mar. 20, 2009, nowU.S. Pat. No. 7,708,656, which is a continuation-in-part of U.S. patentapplication Ser. No. 11/972,240, filed Jan. 10, 2008, now U.S. Pat. No.7,722,482. U.S. patent application Ser. No. 12/423,921 is also acontinuation-in-part of Ser. No. 12/407,865, filed Mar. 20, 2009, nowU.S. Pat. No. 7,713,145, which is a continuation-in-part of U.S. patentapplication Ser. No. 11/972,240, filed Jan. 10, 2008, now U.S. Pat. No.7,722,482. The entire disclosure of each of these related applicationsis hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to multi-piece golf balls havinga solid core and multi-layered cover. In one embodiment, themulti-layered cover is a two-layer cover including inner and outer coverlayers. In another preferred embodiment, there is a three-layer coverincluding inner, intermediate, and outer cover layers. At least one ofthe cover layers comprises a thermoplastic composition and preferablythe composition comprises an ethylene acid copolymer ionomer andplasticizer.

Brief Review of the Related Art

Multi-layered, solid golf balls are used today by recreational andprofessional golfers. In general, these golf balls contain an inner coreprotected by a cover. The core acts as the primary engine for the balland the cover protects the core and helps provide the ball withdurability and wear-resistance. The core and cover may be single ormulti-layered. For example, three-piece golf balls having an inner core,inner cover layer, and outer cover layer are popular. In otherinstances, golfers will use a four-piece ball containing a dual-core(inner core and surrounding outer-core layer) and dual-cover (innercover layer and surrounding outer cover layer). Intermediate layer(s)may be disposed between the core and cover layers to impart variousproperties. Thus, five-piece and even six-piece balls can be made.Normally, the core layers are made of a natural or synthetic rubbermaterial or an ionomer polymer. These ionomer polymers are typicallycopolymers of ethylene and methacrylic acid or acrylic acid that arepartially or fully neutralized. In particular, highly neutralizedpolymer (HNP) compositions may be used to form a core layer. Metal ionssuch as sodium, lithium, zinc, and magnesium are commonly used toneutralize the acid groups in the copolymer.

Such ethylene acid copolymer ionomer resins generally have gooddurability and toughness. These ionomers may be used to make cover,intermediate, and core layers for the golf ball. When used as a corematerial, the ionomer resin helps impart a higher initial velocity tothe golf ball. When used as a cover material, the ionomer resin helpsimpart impact durability, wear-resistance, and cut/shear-resistance tothe golf ball.

Many golf balls used today have multi-layered covers comprising an innercover and surrounding outer cover layer. For example, the inner covermay be made of a relatively hard material such as the above-describedethylene acid copolymer ionomer resin. Meanwhile, the outer cover layermay be made of a relatively soft polyurethane or polyurethanecomposition. Also, three-layered covers, wherein the cover structureincludes an inner cover, intermediate cover, and outer cover layer maybe made. For example, Sullivan, US Patent Application Publication2002/0151380 discloses a golf ball having a core and cover wherein thecover comprises: a) an inner cover layer having a first thickness andbeing disposed directly about the core; b) an outer cover layer having asecond thickness no greater than about 0.050 inches; and c) anintermediate cover layer having a third thickness and being disposedbetween the inner and outer cover layers; wherein the outer cover layercomprises a composition formed of a reactive liquid material (thermosetmaterial comprising polyurethane, polyurea, polyurethane ionomer, epoxy,or a mixture thereof) and the combination of the first, second, andthird thickness is no greater than about 0.125 inches.

Sullivan et al., US Patent Application Publication 2004/0235587discloses a golf ball having a core and a cover comprising: an innercover layer; an outer cover layer having a material hardness of 60 ShoreD or less; and an intermediate cover layer disposed between the innerand outer cover layers. At least two of the inner, intermediate, andouter cover layers comprise a non-ionomeric material. Preferably, theouter cover layer comprises a polyurethane, a polyurea, a copolymer of apolyurethane, a copolymer of a polyurea, or an interpenetrating polymernetwork.

Although some ethylene acid copolymer ionomer compositions may besomewhat effective for making certain components and layers in a golfball, there is still a need for new compositions that can impart highperformance properties to the ball. Particularly, there is a continuingneed for improved cover constructions in golf balls. The cover materialshould have good impact durability, toughness, and cut/shear-resistance,while helping to provide the ball with high resiliency. The covermaterial, however, should not be excessively hard and stiff so thatproperties such as feel, softness, and spin control are sacrificed. Thepresent invention provides golf balls having an optimum combination ofproperties.

SUMMARY OF THE INVENTION

The present invention generally relates to multi-layered golf balls andmore particularly to golf balls having at least one layer made ofthermoplastic ethylene acid copolymer/plasticizer compositions. In oneversion, the ball comprises a core having at least one layer and atwo-layered cover assembly including an inner cover comprising athermoplastic material and a surrounding outer cover. Preferably, thethermoplastic composition comprises: i) an acid copolymer of ethyleneand an α,β-unsaturated carboxylic acid, optionally including a softeningmonomer selected from the group consisting of alkyl acrylates andmethacrylates; ii) a plasticizer; and iii) a cation source present in anamount sufficient to neutralize from about 0% to about 100% of all acidgroups present in the composition. In one embodiment, the inner coverlayer has a Shore D midpoint hardness in the range of about 15 to about60 Shore D, and the outer cover layer has Shore D surface hardness inthe range of about 55 to about 75 Shore D, wherein the hardness of theouter cover layer is greater than the hardness of the inner cover layer.

Various plasticizers may be used in the thermoplastic composition. Inone particularly preferred version, the thermoplastic compositioncomprises a fatty acid ester, particularly an alkyl oleate, and moreparticularly ethyl oleate. Preferably, the thermoplastic compositioncomprises about 3 to about 50% by weight plasticizer, more preferablyabout 8 to about 42%, and even more preferably about 10 to about 30%,plasticizer based on weight of composition.

In another version, the ball comprises a core having at least one layerand a two-layered cover assembly including an inner cover comprising anethylene acid copolymer thermoplastic material as described above and asurrounding outer cover. In this embodiment, the inner cover layer has aShore D midpoint hardness in the range of about 55 to about 75 Shore D,and the outer cover layer has Shore D surface hardness in the range ofabout 15 to about 60 Shore D, wherein the hardness of the outer coverlayer is less than the hardness of the inner cover layer.

The ethylene acid copolymer/plasticizer compositions of this inventionmay be used to form one or more core, intermediate, or cover layers.These compositions have a good combination of properties includingCoefficient of Restitution (CoR) and compression so they can be used tomake various golf ball layers. For example, a molded sphere comprisingthe thermoplastic composition of this invention having a Coefficient ofRestitution of at least about 0.750, preferably at least about 0.800;and a Shore C surface hardness of about 10 to about 75, preferably about20 to about 60 can be made.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention areset forth in the appended claims. However, the preferred embodiments ofthe invention, together with further objects and attendant advantages,are best understood by reference to the following detailed descriptionin connection with the accompanying drawings in which:

FIG. 1 is a graph showing the Coefficient of Restitution (COR) ofcommercially-available samples and ethylene acid copolymer/plasticizersamples of this invention plotted against the DCM Compression (DCM) ofthe respective samples and includes an Index Line;

FIG. 2 is a graph showing the Coefficient of Restitution (COR) ofadditional commercially-available samples and ethylene acidcopolymer/plasticizer samples of this invention plotted against the DCMCompression (DCM) of the respective samples;

FIG. 3 is a graph showing the Soft and Fast Index (SFI) values for theethylene acid copolymer/plasticizer samples plotted in FIGS. 1 and 2plotted against the concentration of plasticizer in the respectivecompositions;

FIG. 4 is a cross-sectional view of a two-piece golf ball having a coreand cover made in accordance with the present invention;

FIG. 5 is a cross-sectional view of a three-piece golf ball having asingle-layered core and two-layered cover made in accordance with thepresent invention;

FIG. 6 is a cross-sectional view of a four-piece golf ball having atwo-layered core and two-layered cover made in accordance with thepresent invention;

FIG. 7 is a cross-sectional view of a four-piece golf ball having asingle-layered core and three-layered cover made in accordance with thepresent invention; and

FIG. 8 is a cross-sectional view of a five-piece golf ball having atwo-layered core and three-layered cover with inner, intermediate, andouter cover layers made in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Golf Ball Constructions

Golf balls having various constructions may be made in accordance withthis invention. For example, golf balls having one-piece, two-piece,three-piece, four-piece, and five or more-piece constructions with theterm “piece” referring to any core, cover or intermediate layer of agolf ball construction. Representative illustrations of such golf ballconstructions are provided and discussed further below. The term,“layer” as used herein means generally any spherical portion of the golfball. More particularly, in one version, a one-piece ball is made usingthe inventive composition as the entire golf ball excluding any paint orcoating and indicia applied thereon. In a second version, a two-pieceball comprising a single core and a single cover layer is made. In athird version, a three-piece golf ball containing a dual-layered coreand single-layered cover is made. The dual-core includes an inner core(center) and surrounding outer core layer. In another version, athree-piece ball containing a single core layer and two cover layers ismade. In yet another version, a four-piece golf ball containing adual-core and dual-cover (inner cover and outer cover layers) is made.In yet another construction, a four-piece or five-piece golf ballcontaining a dual-core; an inner cover layer, an intermediate cover andan outer cover layer, may be made. In still another construction, afive-piece ball is made containing an innermost core layer (or center),an intermediate core layer, an outer core layer, an inner cover layerand an outer cover layer. The diameter and thickness of the differentlayers along with properties such as hardness and compression may varydepending upon the construction and desired playing performanceproperties of the golf ball. Any one or more of the layers of any of theone, two, three, four, or five, or more-piece (layered) balls describedabove may comprise a plasticized thermoplastic composition as disclosedherein. That is, any of the inner (center) core and/or outer corelayers, and/or inner, intermediate, or outer cover layers may comprise aplasticized composition of this invention.

Also, when more than one thermoplastic layer is used in the golf ball,the thermoplastic composition in the respective layers may be the sameor different, and the composition may have the same or differenthardness values. For example, a dual-layered core assembly may be made,wherein the inner core (center) comprises a first thermoplasticcomposition, and the outer core layer comprises a second thermoplasticcomposition. The first and second compositions may be the same, or therespective compositions may be different. For instance, the plasticizedthermoplastic of this invention may be used in one or both core layers.Preferably, the plasticized thermoplastic composition of this inventionis used to form at least one core layer. Likewise, when more than onethermoset layer is used in the golf ball, the thermoset composition inthe respective layers may be the same or different, and the compositionmay have the same or different hardness values. Furthermore, in someexamples, the thermoplastic material in a particular thermoplastic layermay constitute two, three, or more “sub-layers” of the same or differentthermoplastic composition. That is, each thermoplastic layer can beformed from one or more sub-layers of the same or differentthermoplastic material. In such instances, the thermoplastic layer canbe considered a composite layer made of multiple independent anddistinct component layers. Preferably, at least one of the componentlayers comprises the plasticized thermoplastic composition of thisinvention.

Highly-Neutralized Polymer Compositions

Highly-neutralized polymer compositions (HNPs) may be used to form anycover layer in accordance with the present invention. Suitable HNPcompositions, which are plasticized per this invention, comprise an HNPand optionally melt-flow modifier(s), additive(s), and/or filler(s). Forpurposes of the present disclosure, “HNP” refers to an acid polymerafter at least 70%, preferably at least 80%, more preferably at least90%, more preferably at least 95%, and even more preferably 100%, of theacid groups present are neutralized. It is understood that the HNP maybe a blend of two or more HNPs. Preferred acid polymers are copolymersof an α-olefin and a C₃-C₈ α,β-ethylenically unsaturated carboxylicacid, optionally including a softening monomer. The α-olefin ispreferably selected from ethylene and propylene. The acid is preferablyselected from (meth)acrylic acid, ethacrylic acid, maleic acid, crotonicacid, fumaric acid, and itaconic acid. (Meth)acrylic acid isparticularly preferred. The optional softening monomer is preferablyselected from alkyl (meth)acrylate, wherein the alkyl groups have from 1to 8 carbon atoms. Preferred acid copolymers include, but are notlimited to, those wherein the α-olefin is ethylene, the acid is(meth)acrylic acid, and the optional softening monomer is selected from(meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, methyl(meth)acrylate, and ethyl (meth)acrylate. Particularly preferred acidcopolymers include, but are not limited to, ethylene/(meth)acrylicacid/n-butyl acrylate, ethylene/(meth)acrylic acid/methyl acrylate, andethylene/(meth)acrylic acid/ethyl acrylate.

Suitable acid copolymers for forming the HNP also include acid polymersthat are already partially neutralized. Examples of suitable partiallyneutralized acid copolymers include, but are not limited to, Surlyn®ionomers, commercially available from E. I. du Pont de Nemours andCompany; AClyn® ionomers, commercially available from HoneywellInternational Inc.; and Iotek® ionomers, commercially available fromExxonMobil Chemical Company. Also suitable are DuPont® HPF 1000 andDuPont® HPF 2000, ionomeric materials commercially available from E. I.du Pont de Nemours and Company. In some embodiments, very low modulusionomer- (“VLMI-”) type ethylene-acid copolymers are particularlysuitable for forming the HNP, such as Surlyn® 6320, Surlyn® 8120,Surlyn® 8320, and Surlyn® 9320, commercially available from E. I. duPont de Nemours and Company.

The α-olefin is typically present in the acid copolymer in an amount of15 wt % or greater, or 25 wt % or greater, or 40 wt % or greater, or 60wt % or greater, based on the total weight of the acid copolymer. Theacid is typically present in the acid copolymer in an amount within arange having a lower limit of 1 or 2 or 4 or 6 or 8 or 10 or 12 or 15 or16 or 20 wt % and an upper limit of 20 or 25 or 26 or 30 or 35 or 40 wt%, based on the total weight of the acid copolymer. The optionalsoftening monomer is typically present in the acid copolymer in anamount within a range having a lower limit of 0 or 1 or 3 or 5 or 11 or15 or 20 wt % and an upper limit of 23 or 25 or 30 or 35 or 50 wt %,based on the total weight of the acid copolymer.

Additional suitable acid copolymers are more fully described, forexample, in U.S. Pat. Nos. 5,691,418, 6,562,906, 6,653,382, 6,777,472,6,762,246, 6,815,480, and 6,953,820 and U.S. Patent ApplicationPublication Nos. 2005/0148725, 2005/0049367, 2005/0020741, 2004/0220343,and 2003/0130434, the entire disclosures of which are herebyincorporated herein by reference.

The HNP is formed by reacting the acid copolymer with a sufficientamount of cation source, optionally in the presence of a high molecularweight organic acid or salt thereof, such that at least 70%, preferablyat least 80%, more preferably at least 90%, more preferably at least95%, and even more preferably 100%, of all acid groups present areneutralized. The resulting HNP composition is plasticized with aplasticizer. Suitable plasticizers are described further below. In aparticular embodiment, the cation source is present in an amountsufficient to neutralize, theoretically, greater than 100%, or 105% orgreater, or 110% or greater, or 115% or greater, or 120% or greater, or125% or greater, or 200% or greater, or 250% or greater of all acidgroups present in the composition. The acid copolymer can be reactedwith the optional high molecular weight organic acid or salt thereof andthe cation source simultaneously, or the acid copolymer can be reactedwith the optional high molecular weight organic acid or salt thereofprior to the addition of the cation source.

Suitable cation sources include metal ions and compounds of alkalimetals, alkaline earth metals, and transition metals; metal ions andcompounds of rare earth elements; and combinations thereof. Preferredcation sources are metal ions and compounds of magnesium, sodium,potassium, cesium, calcium, barium, manganese, copper, zinc, tin,lithium, and rare earth metals. The acid copolymer may be at leastpartially neutralized prior to contacting the acid copolymer with thecation source to form the HNP. Methods of preparing ionomers, and theacid copolymers on which ionomers are based, are disclosed, for example,in U.S. Pat. Nos. 3,264,272, and 4,351,931, and U.S. Patent ApplicationPublication No. 2002/0013413.

Suitable high molecular weight organic acids, for both the metal saltand as a component of the ester plasticizer, are aliphatic organicacids, aromatic organic acids, saturated monofunctional organic acids,unsaturated monofunctional organic acids, multi-unsaturatedmonofunctional organic acids, and dimerized derivatives thereof.Particular examples of suitable organic acids include, but are notlimited to, caproic acid, caprylic acid, capric acid, lauric acid,stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid,myristic acid, benzoic acid, palmitic acid, phenylacetic acid,naphthalenoic acid, dimerized derivatives thereof, and combinationsthereof. Salts of high molecular weight organic acids comprise thesalts, particularly the barium, lithium, sodium, zinc, bismuth,chromium, cobalt, copper, potassium, strontium, titanium, tungsten,magnesium, and calcium salts, of aliphatic organic acids, aromaticorganic acids, saturated monofunctional organic acids, unsaturatedmonofunctional organic acids, multi-unsaturated monofunctional organicacids, dimerized derivatives thereof, and combinations thereof. Suitableorganic acids and salts thereof are more fully described, for example,in U.S. Pat. No. 6,756,436, the entire disclosure of which is herebyincorporated herein by reference. In a particular embodiment, the HNPcomposition comprises an organic acid salt in an amount of 20 phr orgreater, or 25 phr or greater, or 30 phr or greater, or 35 phr orgreater, or 40 phr or greater.

The plasticized HNP compositions of the present invention optionallycontain one or more melt-flow modifiers. The amount of melt-flowmodifier in the composition is readily determined such that themelt-flow index of the composition is at least 0.1 g/10 min, preferablyfrom 0.5 g/10 min to 10.0 g/10 min, and more preferably from 1.0 g/10min to 6.0 g/10 min, as measured using ASTM D-1238, condition E, at 190°C., using a 2160 gram weight.

It is not required that a conventional melt-flow modifier be added tothe plasticized HNP composition of this invention. Such melt-flowmodifiers are optional. If a melt-flow modifier is added, it may beselected from the group of traditional melt-flow modifiers including,but not limited to, the high molecular weight organic acids and saltsthereof disclosed above, polyamides, polyesters, polyacrylates,polyurethanes, polyethers, polyureas, polyhydric alcohols, andcombinations thereof. Also suitable are the non-fatty acid melt-flowmodifiers disclosed in U.S. Pat. Nos. 7,365,128 and 7,402,629, theentire disclosures of which are hereby incorporated herein by reference.However, as discussed above, certain plasticizers are added to thecomposition of this invention, and it is recognized that suchplasticizers may modify the melt-flow of the composition in someinstances.

The plasticized HNP compositions of the present invention optionallyinclude additive(s) and/or filler(s) in an amount within a range havinga lower limit of 0 or 5 or 10 wt %, and an upper limit of 15 or 20 or 25or 30 or 50 wt %, based on the total weight of the composition. Suitableadditives and fillers include, but are not limited to, chemical blowingand foaming agents, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, defoamingagents, processing aids, mica, talc, nano-fillers, antioxidants,stabilizers, softening agents, fragrance components, impact modifiers,TiO₂, acid copolymer wax, surfactants, and fillers, such as zinc oxide,tin oxide, barium sulfate, zinc sulfate, calcium oxide, calciumcarbonate, zinc carbonate, barium carbonate, clay, tungsten, tungstencarbide, silica, lead silicate, regrind (recycled material), andmixtures thereof. Suitable additives are more fully disclosed, forexample, in U.S. Patent Application Publication No. 2003/0225197, theentire disclosure of which is hereby incorporated herein by reference.

In some embodiments, the plasticized HNP composition is a “moistureresistant” HNP composition, i.e., having a moisture vapor transmissionrate (“MVTR”) of 8 g-mil/100 in²/day or less (i.e., 3.2 g-mm/m²·day orless), or 5 g-mil/100 in²/day or less (i.e., 2.0 g-mm/m²·day or less),or 3 g-mil/100 in²/day or less (i.e., 1.2 g-mm/m²·day or less), or 2g-mil/100 in²/day or less (i.e., 0.8 g-mm/m²·day or less), or 1g-mil/100 in²/day or less (i.e., 0.4 g-mm/m²·day or less), or less than1 g-mil/100 in²/day (i.e., less than 0.4 g-mm/m²·day). Suitable moistureresistant HNP compositions are disclosed, for example, in U.S. PatentApplication Publication Nos. 2005/0267240, 2006/0106175, and2006/0293464, the entire disclosures of which are hereby incorporatedherein by reference.

The plasticized HNP compositions of the present invention are notlimited by any particular method or any particular equipment for makingthe compositions. In a preferred embodiment, the composition is preparedby the following process. The acid copolymer(s), plasticizers, optionalmelt-flow modifier(s), and optional additive(s)/filler(s) aresimultaneously or individually fed into a melt extruder, such as asingle or twin screw extruder. Other suitable methods for incorporatingthe plasticizer into the composition are described further below. Asuitable amount of cation source is then added such that at least 70%,or at least 80%, or at least 90%, or at least 95%, or at least 100%, ofall acid groups present are neutralized. Optionally, the cation sourceis added in an amount sufficient to neutralize, theoretically, 105% orgreater, or 110% or greater, or 115% or greater, or 120% or greater, or125% or greater, or 200% or greater, or 250% or greater of all acidgroups present in the composition. The acid copolymer may be at leastpartially neutralized prior to the above process. The components areintensively mixed prior to being extruded as a strand from the die-head.

The HNP composition, which will be plasticized with specificplasticizers as described in detail below, optionally comprises at leastone additional copolymer component selected from partially neutralizedionomers as disclosed, for example, in U.S. Patent ApplicationPublication No. 2006/0128904, the entire disclosure of which is herebyincorporated herein by reference; bimodal ionomers, such as thosedisclosed in U.S. Patent Application Publication No. 2004/0220343 andU.S. Pat. Nos. 6,562,906, 6,762,246, 7,273,903, 8,193,283, 8,410,219,and 8,410,220, the entire disclosures of which are hereby incorporatedherein by reference, and particularly Surlyn® AD 1043, 1092, 1022, andSEP 1856-1 ionomer resins, commercially available from E. I. du Pont deNemours and Company; ionomers modified with rosins, such as thosedisclosed in U.S. Patent Application Publication No. 2005/0020741, theentire disclosure of which is hereby incorporated by reference; soft andresilient ethylene copolymers, such as those disclosed U.S. PatentApplication Publication No. 2003/0114565, the entire disclosure of whichis hereby incorporated herein by reference; polyolefins, such as linear,branched, or cyclic, C₂-C₄₀ olefins, particularly polymers comprisingethylene or propylene copolymerized with one or more C₂-C₄₀ olefins,C₃-C₂₀ α-olefins, or C₃-C₁₀ α-olefins; polyamides; polyesters;polyethers; polycarbonates; polysulfones; polyacetals; polylactones;acrylonitrile-butadiene-styrene resins; polyphenylene oxide;polyphenylene sulfide; styrene-acrylonitrile resins; styrene maleicanhydride; polyimides; aromatic polyketones; ionomers and ionomericprecursors, acid copolymers, and conventional HNPs, such as thosedisclosed in U.S. Pat. Nos. 6,756,436, 6,894,098, and 6,953,820, theentire disclosures of which are hereby incorporated herein by reference;polyurethanes; grafted and non-grafted metallocene-catalyzed polymers,such as single-site catalyst polymerized polymers, high crystalline acidpolymers, cationic ionomers, and combinations thereof.

Other polymer components that may be included in the plasticized HNPcomposition include, for example, natural and synthetic rubbers,including, but not limited to, ethylene propylene rubber (“EPR”),ethylene propylene diene rubber (“EPDM”), styrenic block copolymerrubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where “S” isstyrene, “I ” is isobutylene, and “B” is butadiene), butyl rubber,halobutyl rubber, copolymers of isobutylene and para-alkylstyrene,halogenated copolymers of isobutylene and para-alkylstyrene, naturalrubber, polyisoprene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber (such as ethylene-alkyl acrylatesand ethylene-alkyl methacrylates, and, more specifically, ethylene-ethylacrylate, ethylene-methyl acrylate, and ethylene-butyl acrylate),chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber,and polybutadiene rubber (cis and trans). Additional suitable blendpolymers include those described in U.S. Pat. No. 5,981,658, for exampleat column 14, lines 30 to 56, the entire disclosure of which is herebyincorporated herein by reference.

The blend may be produced by post-reactor blending, by connectingreactors in series to make reactor blends, or by using more than onecatalyst in the same reactor to produce multiple species of polymer. Thepolymers may be mixed prior to being put into an extruder, or they maybe mixed in an extruder. In a particular embodiment, the plasticized HNPcomposition comprises an acid copolymer and an additional polymercomponent, wherein the additional polymer component is a non-acidpolymer present in an amount of greater than 50 wt %, or an amountwithin a range having a lower limit of 50 or 55 or 60 or 65 or 70 and anupper limit of 80 or 85 or 90, based on the combined weight of the acidcopolymer and the non-acid polymer. In another particular embodiment,the plasticized HNP composition comprises an acid copolymer and anadditional polymer component, wherein the additional polymer componentis a non-acid polymer present in an amount of less than 50 wt %, or anamount within a range having a lower limit of 10 or 15 or 20 or 25 or 30and an upper limit of 40 or 45 or 50, based on the combined weight ofthe acid copolymer and the non-acid polymer.

The plasticized HNP compositions of the present invention, in the neat(i.e., unfilled) form, preferably have a specific gravity of 0.90 g/ccto 1.00 g/cc, more preferably 0.95 g/cc to 0.99 g/cc. Any suitablefiller, flake, fiber, particle, or the like, of an organic or inorganicmaterial may be added to the HNP composition to increase or decrease thespecific gravity, particularly to adjust the weight distribution withinthe golf ball, as further disclosed in U.S. Pat. Nos. 6,494,795,6,547,677, 6,743,123, 7,074,137, and 6,688,991, the entire disclosuresof which are hereby incorporated herein by reference. The term,“specific gravity” as used herein, has its ordinary and customarymeaning, that is, the ratio of the density of a substance to the densityof water at 4° C., and the density of water at this temperature is 1g/cm³.

In one particular embodiment, the plasticized HNP composition isselected from the relatively “soft” HNP compositions disclosed in U.S.Pat. No. 7,468,006, the entire disclosure of which is herebyincorporated herein by reference, and the low modulus HNP compositionsdisclosed in U.S. Pat. No. 7,207,903, the entire disclosure of which ishereby incorporated herein by reference. In a particular aspect of thisembodiment, a sphere formed from the HNP composition has a compressionof 80 or less, or 70 or less, or 65 or less, or 60 or less, or 50 orless, or 40 or less, or 30 or less, or 20 or less. In another particularaspect of this embodiment, the plasticized HNP composition has amaterial hardness within a range having a lower limit of 40 or 50 or 55Shore C and an upper limit of 70 or 80 or 87 Shore C, or a materialhardness of 55 Shore D or less, or a material hardness within a rangehaving a lower limit of 10 or 20 or 30 or 37 or 39 or 40 or 45 Shore Dand an upper limit of 48 or 50 or 52 or 55 or 60 or 80 Shore D. In yetanother particular aspect of this embodiment, the plasticized HNPcomposition comprises an HNP having a modulus within a range having alower limit of 1,000 or 5,000 or 10,000 psi and an upper limit of 17,000or 25,000 or 28,000 or 30,000 or 35,000 or 45,000 or 50,000 or 55,000psi, as measured using a standard flex bar according to ASTM D790-B.

In a second particular embodiment, the plasticized HNP composition isselected from the relatively “hard” HNP compositions disclosed in U.S.Pat. No. 7,468,006, the entire disclosure of which is herebyincorporated herein by reference, and the high modulus HNP compositionsdisclosed in U.S. Pat. No. 7,207,903, the entire disclosure of which ishereby incorporated herein by reference. In a particular aspect of thisembodiment, a sphere formed from the plasticized HNP composition has acompression of 70 or greater, or 80 or greater, or a compression withina range having a lower limit of 70 or 80 or 90 or 100 and an upper limitof 110 or 130 or 140. In another particular aspect of this embodiment,the HNP composition has a material hardness of 35 Shore D or greater, or45 Shore D or greater, or a material hardness within a range having alower limit of 45 or 50 or 55 or 57 or 58 or 60 or 65 or 70 or 75 ShoreD and an upper limit of 75 or 80 or 85 or 90 or 95 Shore D. In yetanother particular aspect of this embodiment, the plasticized HNPcomposition comprises an HNP having a modulus within a range having alower limit of 25,000 or 27,000 or 30,000 or 40,000 or 45,000 or 50,000or 55,000 or 60,000 psi and an upper limit of 72,000 or 75,000 or100,000 or 150,000 psi, as measured using a standard flex bar accordingto ASTM D790-B. Suitable HNP compositions are further disclosed, forexample, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,777,472, 6,815,480,6,894,098, 6,919,393, 6,953,820, 6,994,638, 7,375,151, the entiredisclosures of which are hereby incorporated herein by reference.Plasticizers, as described further below, are added to theabove-described soft and hard and other HNP compositions.

In a particular embodiment, the HNP composition is formed by blending anacid copolymer, a non-acid polymer, a cation source, and a fatty acid ormetal salt thereof. The resulting HNP composition is plasticized with aplasticizer as described further below. For purposes of the presentinvention, maleic anhydride modified polymers are defined herein as anon-acid polymer despite having anhydride groups that can ring-open tothe acid form during processing of the polymer to form the HNPcompositions herein. The maleic anhydride groups are grafted onto apolymer, are present at relatively very low levels, and are not part ofthe polymer backbone, as is the case with the acid polymers, which areexclusively E/X and E/X/Y copolymers of ethylene and an acid,particularly methacrylic acid and acrylic acid.

In a particular aspect of this embodiment, the acid copolymer isselected from ethylene-acrylic acid and ethylene-methacrylic acidcopolymers, optionally containing a softening monomer selected fromn-butyl acrylate, iso-butyl acrylate, and methyl acrylate. The acidcopolymer preferably has an acid content with a range having a lowerlimit of 2 or 10 or 15 or 16 weight % and an upper limit of 20 or 25 or26 or 30 weight %.

The non-acid polymer is preferably selected from the group consisting ofpolyolefins, polyamides, polyesters, polyethers, polyurethanes,metallocene-catalyzed polymers, single-site catalyst polymerizedpolymers, ethylene propylene rubber, ethylene propylene diene rubber,styrenic block copolymer rubbers, alkyl acrylate rubbers, andfunctionalized derivatives thereof.

In another particular aspect of this embodiment, the non-acid polymer isan elastomeric polymer. Suitable elastomeric polymers include, but arenot limited to:

(a) ethylene-alkyl acrylate polymers, particularly polyethylene-butylacrylate, polyethylene-methyl acrylate, and polyethylene-ethyl acrylate;

(b) metallocene-catalyzed polymers;

(c) ethylene-butyl acrylate-carbon monoxide polymers and ethylene-vinylacetate-carbon monoxide polymers;

(d) polyethylene-vinyl acetates;

(e) ethylene-alkyl acrylate polymers containing a cure site monomer;

(f) ethylene-propylene rubbers and ethylene-propylene-diene monomerrubbers;

(g) olefinic ethylene elastomers, particularly ethylene-octene polymers,ethylene-butene polymers, ethylene-propylene polymers, andethylene-hexene polymers;

(h) styrenic block copolymers;

(i) polyester elastomers;

(j) polyamide elastomers;

(k) polyolefin rubbers, particularly polybutadiene, polyisoprene, andstyrene-butadiene rubber; and

(l) thermoplastic polyurethanes.

Examples of particularly suitable commercially available non-acidpolymers include, but are not limited to, Lotader® ethylene-alkylacrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, andparticularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900commercially available from Arkema Corporation; Elvaloy® ACethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC2116, AC3117, AC3427, and AC34035, commercially available from E. I. duPont de Nemours and Company; Fusabond® elastomeric polymers, such asethylene vinyl acetates, polyethylenes, metallocene-catalyzedpolyethylenes, ethylene propylene rubbers, and polypropylenes, andparticularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614,M603, E100, E158, E226, E265, E528, and E589, commercially availablefrom E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenesand ethylene maleic anhydride copolymers, and particularly A-C 5180, A-C575, A-C 573, A-C 655, and A-C 395, commercially available fromHoneywell; Nordel® IP rubber, Elite® polyethylenes, Engage® elastomers,and Amplify® functional polymers, and particularly Amplify® GR 207, GR208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA 100, commerciallyavailable from The Dow Chemical Company; Enable® metallocenepolyethylenes, Exact® plastomers, Vistamaxx® propylene-based elastomers,and VistaIon® EPDM rubber, commercially available from ExxonMobilChemical Company; Starflex® metallocene linear low density polyethylene,commercially available from LyondellBasell; Elvaloy® HP4051, HP441,HP661 and HP662 ethylene-butyl acrylate-carbon monoxide polymers andElvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbon monoxidepolymers, commercially available from E. I. du Pont de Nemours andCompany; Evatane® ethylene-vinyl acetate polymers having a vinyl acetatecontent of from 18 to 42%, commercially available from ArkemaCorporation; Elvax® ethylene-vinyl acetate polymers having a vinylacetate content of from 7.5 to 40%, commercially available from E. I. duPont de Nemours and Company; Vamac® G terpolymer of ethylene,methylacrylate and a cure site monomer, commercially available from E.I. du Pont de Nemours and Company; Vistalon®EPDM rubbers, commerciallyavailable from ExxonMobil Chemical Company; Kraton® styrenic blockcopolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT,commercially available from Kraton Performance Polymers Inc.; Septon®styrenic block copolymers, commercially available from Kuraray Co.,Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069,and 5556, commercially available from E. I. du Pont de Nemours andCompany; Riteflex® polyester elastomers, commercially available fromCelanese Corporation; Pebax® thermoplastic polyether block amides, andparticularly Pebax® 2533, 3533, 4033, and 5533, commercially availablefrom Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify®ethylene-propylene copolymer elastomers, and Infuse® olefin blockcopolymers, commercially available from The Dow Chemical Company;Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially availablefrom ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularlyRoyaltuf®498 maleic anhydride modified polyolefin based on an amorphousEPDM and Royaltuf®485 maleic anhydride modified polyolefin based on ansemi-crystalline EPDM, commercially available from Chemtura Corporation.

In the plasticized HNP compositions, the acid copolymer and non-acidpolymer are combined and reacted with a cation source, such that atleast 80% of all acid groups present are neutralized. The resultingplasticized HNP composition also includes a plasticizer as describedfurther below. The present invention is not meant to be limited by aparticular order for combining and reacting the acid polymer, non-acidpolymer and cation source. In a particular embodiment, the fatty acid ormetal salt thereof is used in an amount such that the fatty acid ormetal salt thereof is present in the HNP composition in an amount offrom 10 wt % to 60 wt %, or within a range having a lower limit of 10 or20 or 30 or 40 wt % and an upper limit of 40 or 50 or 60 wt %, based onthe total weight of the HNP composition. Suitable cation sources andfatty acids and metal salts thereof are further disclosed above.

In another particular aspect of this embodiment, the acid copolymer isan ethylene-acrylic acid copolymer having an acid content of 19 wt % orgreater, the non-acid polymer is a metallocene-catalyzed ethylene-butenecopolymer, optionally modified with maleic anhydride, the cation sourceis magnesium, and the fatty acid or metal salt thereof is magnesiumoleate present in the composition in an amount of 20 to 50 wt %, basedon the total weight of the composition. This preferred HNP compositionis treated with a plasticizer as described further below.

As discussed above, the ethylene acid copolymer may be blended withother materials including, but not limited to, partially- andfully-neutralized ionomers optionally blended with a maleicanhydride-grafted non-ionomeric polymer, graft copolymers of ionomer andpolyamide, and the following non-ionomeric polymers, includinghomopolymers and copolymers thereof, as well as their derivatives thatare compatibilized with at least one grafted or copolymerized functionalgroup, such as maleic anhydride, amine, epoxy, isocyanate, hydroxyl,sulfonate, phosphonate, and the like. Other suitable materials that maybe blended with the ethylene acid copolymer include, for example thefollowing polymers (including homopolymers, copolymers, and derivativesthereof):

-   -   (a) polyesters, particularly those modified with a        compatibilizing group such as sulfonate or phosphonate,        including modified poly(ethylene terephthalate), modified        poly(butylene terephthalate), modified poly(propylene        terephthalate), modified poly(trimethylene terephthalate),        modified poly(ethylene naphthenate), and those disclosed in U.S.        Pat. Nos. 6,353,050, 6,274,298, and 6,001,930, the entire        disclosures of which are hereby incorporated herein by        reference, and blends of two or more thereof;    -   (b) polyamides, polyamide-ethers, and polyamide-esters, and        those disclosed in U.S. Pat. Nos. 6,187,864, 6,001,930, and        5,981,654, the entire disclosures of which are hereby        incorporated herein by reference, and blends of two or more        thereof;    -   (c) polyurethanes, polyureas, polyurethane-polyurea hybrids, and        blends of two or more thereof;    -   (d) fluoropolymers, such as those disclosed in U.S. Pat. Nos.        5,691,066, 6,747,110 and 7,009,002, the entire disclosures of        which are hereby incorporated herein by reference, and blends of        two or more thereof;    -   (e) non-ionomeric acid polymers, such as E/X- and E/X/Y-type        polymers, wherein E is an olefin (e.g., ethylene), X is a        carboxylic acid such as acrylic, methacrylic, crotonic, maleic,        fumaric, or itaconic acid, and Y is a softening comonomer such        as vinyl esters of aliphatic carboxylic acids wherein the acid        has from 2 to 10 carbons, alkyl ethers wherein the alkyl group        has from 1 to 10 carbons, and alkyl alkylacrylates such as alkyl        methacrylates wherein the alkyl group has from 1 to 10 carbons;        and blends of two or more thereof;    -   (f) metallocene-catalyzed polymers, such as those disclosed in        U.S. Pat. Nos. 6,274,669, 5,919,862, 5,981,654, and 5,703,166,        the entire disclosures of which are hereby incorporated herein        by reference, and blends of two or more thereof;    -   (g) polystyrenes, such as poly(styrene-co-maleic anhydride),        acrylonitrile-butadiene-styrene, poly(styrene sulfonate),        polyethylene styrene, and blends of two or more thereof;    -   (h) polypropylenes and polyethylenes, particularly grafted        polypropylene and grafted polyethylenes that are modified with a        functional group, such as maleic anhydride of sulfonate, and        blends of two or more thereof;    -   (i) polyvinyl chlorides and grafted polyvinyl chlorides, and        blends of two or more thereof;    -   (j) polyvinyl acetates, preferably having less than about 9% of        vinyl acetate by weight, and blends of two or more thereof;    -   (k) polycarbonates, blends of        polycarbonate/acrylonitrile-butadiene-styrene, blends of        polycarbonate/polyurethane, blends of polycarbonate/polyester,        and blends of two or more thereof;    -   (l) polyvinyl alcohols, and blends of two or more thereof;    -   (m) polyethers, such as polyarylene ethers, polyphenylene        oxides, block copolymers of alkenyl aromatics with vinyl        aromatics and poly(amic ester)s, and blends of two or more        thereof;    -   (n) polyimides, polyetherketones, polyamideimides, and blends of        two or more thereof;    -   (o) polycarbonate/polyester copolymers and blends; and    -   (p) combinations of any two or more of the above thermoplastic        polymers.

Suitable ionomeric compositions comprise one or more acid polymers, eachof which is partially- or fully-neutralized, and optionally additives,fillers, and/or melt-flow modifiers. Suitable acid polymers are salts ofhomopolymers and copolymers of α,β-ethylenically unsaturated mono- ordicarboxylic acids, and combinations thereof, optionally including asoftening monomer, and preferably having an acid content (prior toneutralization) of from 1 wt % to 30 wt %, more preferably from 5 wt %to 20 wt %. The acid polymer is preferably neutralized to 70% or higher,including up to 100%, with a suitable cation source, such as metalcations and salts thereof, organic amine compounds, ammonium, andcombinations thereof. Preferred cation sources are metal cations andsalts thereof, wherein the metal is preferably lithium, sodium,potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum,manganese, nickel, chromium, copper, or a combination thereof.

Suitable additives and fillers include, for example, blowing and foamingagents, optical brighteners, coloring agents, fluorescent agents,whitening agents, UV absorbers, light stabilizers, defoaming agents,processing aids, mica, talc, nanofillers, antioxidants, stabilizers,softening agents, fragrance components, impact modifiers, acid copolymerwax, surfactants; inorganic fillers, such as zinc oxide, titaniumdioxide, tin oxide, calcium oxide, magnesium oxide, barium sulfate, zincsulfate, calcium carbonate, zinc carbonate, barium carbonate, mica,talc, clay, silica, lead silicate, and the like; high specific gravitymetal powder fillers, such as tungsten powder, molybdenum powder, andthe like; regrind, i.e., core material that is ground and recycled; andnano-fillers. Suitable melt-flow modifiers include, for example, fattyacids and salts thereof, polyamides, polyesters, polyacrylates,polyurethanes, polyethers, polyureas, polyhydric alcohols, andcombinations thereof.

Suitable ionomeric compositions include blends of highly neutralizedpolymers (i.e., neutralized to 70% or higher) with partially neutralizedionomers as disclosed, for example, in U.S. Patent ApplicationPublication No. 2006/0128904, the entire disclosure of which is herebyincorporated herein by reference. Suitable ionomeric compositions alsoinclude blends of one or more partially- or fully-neutralized polymerswith additional thermoplastic and thermoset materials, including, butnot limited to, non-ionomeric acid copolymers, engineeringthermoplastics, fatty acid/salt-based highly neutralized polymers,polybutadienes, polyurethanes, polyureas, polyesters,polycarbonate/polyester blends, thermoplastic elastomers, maleicanhydride-grafted metallocene-catalyzed polymers, and other conventionalpolymeric materials. Suitable ionomeric compositions are furtherdisclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436,6,777,472, 6,894,098, 6,919,393, and 6,953,820, the entire disclosuresof which are hereby incorporated herein by reference.

Examples of commercially available thermoplastics suitable for formingcover layers of golf balls disclosed herein include, but are not limitedto, Pebax® thermoplastic polyether block amides, commercially availablefrom Arkema Inc.; Surlyn® ionomer resins, Hytrel® thermoplasticpolyester elastomers, and ionomeric materials sold under the trade namesDuPont® HPF 1000 and HPF 2000, and HPF AD 1035, HPF AD 1035 Soft, HPF AD1040, and HPF AD 1172, all of which are commercially available from E.I. du Pont de Nemours and Company; Iotek® ionomers, commerciallyavailable from ExxonMobil Chemical Company; Amplify® IO ionomers ofethylene acrylic acid copolymers, commercially available from The DowChemical Company; Clarix® ionomer resins, commercially available from A.Schulman Inc.; Elastollan® polyurethane-based thermoplastic elastomers,commercially available from BASF; and Xylex® polycarbonate/polyesterblends, commercially available from SABIC Innovative Plastics.

In a particular embodiment, the plasticized thermoplastic covercomposition comprises a material selected from the group consisting ofpartially- and fully-neutralized ionomers optionally blended with amaleic anhydride-grafted non-ionomeric polymer, polyesters, polyamides,polyethers, and blends of two or more thereof and plasticizer.

In another particular embodiment, the plasticized thermoplastic covercomposition is a blend of two or more ionomers and plasticizer. In aparticular aspect of this embodiment, the thermoplastic composition is a50 wt %/50 wt % blend of two different partially-neutralizedethylene/methacrylic acid polymers.

In another particular embodiment, the plasticized thermoplastic covercomposition is a blend of one or more ionomers and a maleicanhydride-grafted non-ionomeric polymer and plasticizer. In a particularaspect of this embodiment, the non-ionomeric polymer is ametallocene-catalyzed polymer. In another particular aspect of thisembodiment, the ionomer is a partially-neutralized ethylene/methacrylicacid polymer and the non-ionomeric polymer is a maleic anhydride-graftedmetallocene-catalyzed polymer. In another particular aspect of thisembodiment, the ionomer is a partially-neutralized ethylene/methacrylicacid polymer and the non-ionomeric polymer is a maleic anhydride-graftedmetallocene-catalyzed polyethylene.

As discussed above, in one preferred embodiment, at least 70% of theacid groups in the acid copolymer are neutralized, and these materialsare referred to as HNP materials herein. However, it is understood thatother acid copolymer compositions may be used in accordance with thepresent invention. For example, acid copolymer compositions having acidgroups that are neutralized from about 20% to about less than 70% may beused, and these materials may be referred to as partially-neutralizedionomers. For example, the partially-neutralized ionomers may have aneutralization level of about 30% to about 65%, and more particularlyabout 35% to 60%.

Preferred ionomers are salts of O/X- and O/X/Y-type acid copolymers,wherein O is an α-olefin, X is a C₃-C₈ α,β-ethylenically unsaturatedcarboxylic acid, and Y is a softening monomer. Ois preferably selectedfrom ethylene and propylene. X is preferably selected from methacrylicacid, acrylic acid, ethacrylic acid, crotonic acid, and itaconic acid.Methacrylic acid and acrylic acid are particularly preferred. Y ispreferably selected from (meth)acrylate and alkyl (meth)acrylateswherein the alkyl groups have from 1 to 8 carbon atoms, including, butnot limited to, n-butyl (meth)acrylate, isobutyl (meth)acrylate, methyl(meth)acrylate, and ethyl (meth)acrylate.

Preferred O/X and O/X/Y-type copolymers include, without limitation,ethylene acid copolymers, such as ethylene/(meth)acrylic acid,ethylene/(meth)acrylic acid/maleic anhydride, ethylene/(meth)acrylicacid/maleic acid mono-ester, ethylene/maleic acid, ethylene/maleic acidmono-ester, ethylene/(meth)acrylic acid/n-butyl (meth)acrylate,ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate,ethylene/(meth)acrylic acid/methyl (meth)acrylate,ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and thelike. The term, “copolymer,” as used herein, includes polymers havingtwo types of monomers, those having three types of monomers, and thosehaving more than three types of monomers. Preferred α, β-ethylenicallyunsaturated mono- or dicarboxylic acids are (meth)acrylic acid,ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconicacid. (Meth)acrylic acid is most preferred. As used herein,“(meth)acrylic acid” means methacrylic acid and/or acrylic acid.Likewise, “(meth)acrylate” means methacrylate and/or acrylate.

The O/X or O/X/Y-type copolymer is at least partially neutralized with acation source. Suitable cation sources include, but are not limited to,metal ion sources, such as compounds of alkali metals, alkaline earthmetals, transition metals, and rare earth elements; ammonium salts andmonoamine salts; and combinations thereof. Preferred cation sources arecompounds of magnesium, sodium, potassium, cesium, calcium, barium,manganese, copper, zinc, lead, tin, aluminum, nickel, chromium, lithium,and rare earth metals.

Also, as discussed above, it is recognized that the cation source isoptional, and non-neutralized or lowly-neutralized compositions may beused. For example, acid copolymers having 0% to less than 20%neutralization levels may be used. Acid copolymer compositionscontaining plasticizers and having zero percent of the acid groupsneutralized may be used per this invention. Also, acid copolymer ionomercompositions containing plasticizers, wherein 1 to 19% of the acidgroups are neutralized, may be used. Particularly, acid copolymershaving about 3% to about 18% and more particularly about 6% to about 15%neutralization levels may be used in accordance with this invention.

It is also recognized that acid copolymer blends may be preparedincluding, but not limited to, acid copolymer compositions formed from:i) blends of two or more partially-neutralized ionomers; ii) blends oftwo or more highly-neutralized ionomers; iii) blends of two or morenon-neutralized acid copolymers and/or lowly-neutralized ionomers; iv)blends of one or more highly-neutralized ionomers with one or morepartially-neutralized ionomers, and/or lowly-neutralized ionomers,and/or non-neutralized acid copolymers; v) blends ofpartially-neutralized ionomers with one or more highly-neutralizedionomers, and/or lowly-neutralized ionomers, and/or non-neutralized acidcopolymers.

Plasticizers for Making Thermoplastic Compositions

As discussed above, the ethylene acid copolymer compositions of thisinvention contain a plasticizer. Adding the plasticizers helps to reducethe glass transition temperature (Tg) of the composition. The glasstransition in a polymer is a temperature range below which a polymer isrelatively brittle and above which it is rubber-like. In addition tolowering the Tg, the plasticizer may also reduce the tan δ in thetemperature range above the Tg. The Tg of a polymer is measured by aDifferential Scanning calorimeter or a Dynamic Mechanical Analyzer (DMA)and the DMA is used to measure tan δ. The plasticizer may also reducethe hardness and compression of the composition when compared to itsnon-plasticized condition. The effects of adding a plasticizer to theethylene acid copolymer composition on Tg, flex modulus, hardness, andother physical properties are discussed further below.

The ethylene acid copolymer compositions may contain one or moreplasticizers. The plasticizers that may be used in the ethylene acidcopolymer compositions of this invention include, for example,N-butylbenzenesulfonamide (BBSA); N-ethylbenzenesulfonamide (EBSA);N-propylbenzenesulfonamide (PBSA); N-butyl-N-dodecylbenzenesulfonamide(BDBSA); N,N-dimethylbenzenesulfonamide (DMBSA);p-methylbenzenesulfonamide; o,p-toluene sulfonamide; p-toluenesulfonamide; 2-ethylhexyl-4-hydroxybenzoate;hexadecyl-4-hydroxybenzoate; 1-butyl-4-hydroxybenzoate; dioctylphthalate; diisodecyl phthalate; di-(2-ethylhexyl) adipate; andtri-(2-ethylhexyl) phosphate; and blends thereof.

In one preferred version, the plasticizer is selected from the group ofpolytetramethylene ether glycol (available from BASF under thetradename, PolyTHF™ 250); propylene carbonate (available from HuntsmanCorp., under the tradename, Jeffsol™ PC); and/or dipropyleneglycoldibenzoate (available from Eastman Chemical under the tradename,Benzoflex™ 284). Mixtures of these plasticizers also may be used.

Other suitable plasticizer compounds include benzene mono-, di-, andtricarboxylic acid esters. Phthalates such as Bis(2-ethylhexyl)phthalate (DEHP), Diisononyl phthalate (DINP), Di-n-butyl phthalate(DnBP, DBP), Butyl benzyl phthalate (BBP), Diisodecyl phthalate (DIDP),Dioctyl phthalate (DnOP), Diisooctyl phthalate (DIOP), Diethyl phthalate(DEP), Diisobutyl phthalate (DIBP), and Di-n-hexyl phthalate, and blendsthereof are suitable. Iso- and terephthalates such as Dioctylterephthalate and Dinonyl isophthalate may be used. Also appropriate aretrimellitates such as Trimethyl trimellitate (TMTM), Tri-(2-ethylhexyl)trimellitate (TOTM), Tri-(n-octyl,n-decyl) trimellitate,Tri-(heptyl,nonyl) trimellitate, Tri-n-octyl trimellitate; as well asbenzoates, including: 2-ethylhexyl-4-hydroxy benzoate, n-octyl benzoate,methyl benzoate, and ethyl benzoate, and blends thereof.

Also suitable are alkyl diacid esters commonly based on C4-C12 alkyldicarboxylic acids such as adipic, sebacic, azelaic, and maleic acidssuch as: Bis(2-ethylhexyl)adipate (DEHA), Dimethyl adipate (DMAD),Monomethyl adipate (MMAD), Dioctyl adipate (DOA), Dibutyl sebacate(DBS), Dibutyl maleate (DBM), Diisobutyl maleate (DIBM), Dioctylsebacate (DOS), and blends thereof. Also, esters based on glycols,polyglycols and polyhydric alcohols such as poly(ethylene glycol) mono-and di-esters, cyclohexanedimethanol esters, sorbitol derivatives; andtriethylene glycol dihexanoate, diethylene glycol di-2-ethylhexanoate,tetraethylene glycol diheptanoate, and ethylene glycol dioleate, andblends thereof may be used.

Fatty acids, fatty acid salts, fatty acid amides, and fatty acid estersalso may be used in the compositions of this invention. Compounds suchas stearic, oleic, ricinoleic, behenic, myristic, linoleic, palmitic,and lauric acid esters, salts, and mono- and bis-amides can be used.Ethyl oleate, butyl stearate, methyl acetylricinoleate, zinc oleate,ethylene bis-oleamide, and stearyl erucamide are suitable. Suitablefatty acid salts include, for example, metal stearates, erucates,laurates, oleates, palmitates, pelargonates, and the like. For example,fatty acid salts such as zinc stearate, calcium stearate, magnesiumstearate, barium stearate, and the like can be used. Fatty alcohols andacetylated fatty alcohols are also suitable, as are carbonate esterssuch as propylene carbonate and ethylene carbonate. Mixtures of any ofthe plasticizers described herein also may be used in accordance withthis invention. In a particularly preferred version, the fatty acidester is an alkyl oleate selected from the group consisting of methyl,propyl, ethyl, butyl, octyl, and decyl oleates. For example, in oneversion, ethyl oleate is used as the plasticizer. In another version,butyl oleate or octyl oleate is used in the composition. Suitablecommercially-available fatty acids include, for example, SylFat™ FA2Tall Fatty Acid, available from Arizona Chemical. The fatty acidcomposition includes 2% saturated, 50% oleic, 37% linoleic(non-conjugated), and 7% linoleic (conjugated) fatty acids; and 4% otherfatty acids. This fatty acid typically has an acid value in the range of195 to 205 mg KOH/gm.

Glycerol-based esters such as soy-bean, tung, or linseed oils or theirepoxidized derivatives or blends thereof can also be used asplasticizers in the present invention, as can polymeric polyesterplasticizers formed from the esterification reaction of diacids anddiglycols as well as from the ring-opening polymerization reaction ofcaprolactones with diacids or diglycols. Citrate esters and acetylatedcitrate esters are also suitable. Glycerol mono-, di-, and tri-oleatesmay be used per this invention, and in one preferred embodiment,glycerol trioleate is used as the plasticizer.

Dicarboxylic acid molecules containing both a carboxylic acid ester anda carboxylic acid salt can perform suitably as plasticizers. Themagnesium salt of mono-methyl adipate and the zinc salt of mono-octylglutarate are two such examples for this invention. Tri- andtetra-carboxylic acid esters and salts can also be used.

Also envisioned as suitable plasticizers are organophosphate andorganosulfur compounds such as tricresyl phosphate (TCP), tributylphosphate (TBP), octyldiphenyl phosphate, alkyl sulfonic acid phenylesters (ASE); and blends thereof; and sulfonamides such as N-ethyltoluene sulfonamide, N-(2-hydroxypropyl)benzene sulfonamide,N-(n-butyl)benzene sulfonamide. Furthermore, thioester and thioethervariants of the plasticizer compounds mentioned above are suitable.

Non-ester plasticizers such as alcohols, polyhydric alcohols, glycols,polyglycols, and polyethers also are suitable materials forplasticization. Materials such as polytetramethylene ether glycol,poly(ethylene glycol), and poly(propylene glycol), oleyl alcohol, andcetyl alcohol can be used. Hydrocarbon compounds, both saturated andunsaturated, linear or cyclic can be used such as mineral oils,microcrystalline waxes, or low-molecular weight polybutadiene.Halogenated hydrocarbon compounds can also be used.

Other examples of plasticizers that may be used in the ethylene acidcopolymer composition of this invention include butylbenzenesulphonamide(BBSA), ethylhexyl para-hydroxybenzoate (EHPB) and decylhexylpara-hydroxybenzoate (DHPB), as disclosed in Montanari et al., U.S. Pat.No. 6,376,037, the disclosure of which is hereby incorporated byreference.

Esters and alkylamides such as phthalic acid esters including dimethylphthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate,di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate,ditridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate,diisononyl phthalate, ethylphthalylethyl glycolate, butylphthalylbutylglycolate, diundecyl phthalate, di-2-ethylhexyl tetrahydrophthalate asdisclosed in Isobe et al., U.S. Pat. No. 6,538,099, the disclosure ofwhich is hereby incorporated by reference, also may be used.

Jacques et al., U.S. Pat. No. 7,045,185, the disclosure of which ishereby incorporated by reference, discloses sulphonamides such asN-butylbenzenesulphonamide, ethyltoluene-sulphonamide,N-cyclohexyltoluenesulphonamide, 2-ethylhexyl-para-hydroxybenzoate,2-decylhexyl-para-hydroxybenzoate, oligoethyleneoxytetrahydrofurfurylalcohol, or oligoethyleneoxy malonate; esters of hydroxybenzoic acid;esters or ethers of tetrahydrofurfuryl alcohol, and esters of citricacid or hydroxymalonic acid; and these plasticizers also may be used.

Sulfonamides also may be used in the present invention, and thesematerials are described in Fish, Jr. et al., U.S. Pat. No. 7,297,737,the disclosure of which is hereby incorporated by reference. Examples ofsuch sulfonamides include N-alkyl benzenesulfonamides andtoluenesulfonamides, particularly N-butylbenzenesulfonamide,N-(2-hydroxypropyl)benzenesulfonamide, N-ethyl-o-toluenesulfonamide,N-ethyl-p-toluenesulfonamide, o-toluenesulfonamide,p-toluenesulfonamide. Such sulfonamide plasticizers also are describedin Hochstetter et al., US Patent Application Publication 2010/0183837,the disclosure of which is hereby incorporated by reference.

As noted above, the fatty acid esters are particularly preferredplasticizers in the present invention. It has been found that the fattyacid esters perform well as plasticizers in the ethylene acid copolymercomposition. The fatty acid esters have several advantageous properties.For example, the fatty acid esters are compatible with the ethylene acidcopolymers and they tend to blend uniformly and completely with the acidcopolymer. Also, the fatty acid esters tend to improve the resiliencyand/or compression of the composition as discussed further below. Theethylene acid copolymer/plasticizer compositions may contain otheringredients that do not materially affect the basic and novelcharacteristics of the composition. For example, mineral fillers may beadded as discussed above. In one particular version, the compositionconsists essentially of ethylene acid copolymer and plasticizer,particularly a fatty acid ester. In another particular version, thecomposition consists essentially of ethylene acid copolymer, cationsource sufficient to neutralize at least 20% of the acid groups presentin the composition, and plasticizer, particularly a fatty acid ester.

One method of preparing the fatty acid ester involves reacting the fattyacid or mixture of fatty acids with a corresponding alcohol. The alcoholcan be any alcohol including, but not limited to, linear, branched, andcyclic alcohols. The fatty acid ester is commonly a methyl, ethyl,propyl, butyl, octyl, or other alkyl ester of a carboxylic acid thatcontains from 4 to 30 carbon atoms. In the present invention, ethyl,butyl, octyl, and decyl esters and particularly ethyl oleate, butyloleate, and octyl oleate are preferred fatty acid esters because oftheir properties. The carboxylic acid may be saturated or unsaturated.Examples of suitable saturated carboxylic acids, that is, carboxylicacids in which the carbon atoms of the alkyl chain are connected bysingle bonds, include but are not limited to butyric acid (chain lengthof C₄ and molecular weight of 88.1); capric acid (C₁₀ and MW of 172.3);lauric acid (C₁₂ and MW of 200.3); myristic acid (C₁₄ and MW of 228.4);palmitic acid (C₁₆ and MW of 256.4); stearic acid (C₁₈ and MW of 284.5);and behenic acid (C₂₂ and MW of 340.6). Examples of suitable unsaturatedcarboxylic acids, that is, a carboxylic acid in which there is one ormore double bonds between the carbon atoms in the alkyl chain, includebut are not limited to oleic acid (chain length and unsaturation C18:1;and MW of 282.5); linoleic acid (C18:2 and MW of 280.5; linolenic acid(C18:3 and MW of 278.4); and erucic acid (C22:1 and MW of 338.6).

It is believed that the plasticizer should be added in a sufficientamount to the ethylene acid copolymer composition so there is asubstantial change in the stiffness and/or hardness of the ethylene acidcopolymer. Thus, although the concentration of plasticizer may be aslittle as 1% by weight to form some ethylene acid copolymer compositionsper this invention, it is preferred that the concentration be relativelygreater. For example, it is preferred that the concentration of theplasticizer be at least 3 weight percent (wt. %). More particularly, itis preferred that the plasticizer be present in an amount within a rangehaving a lower limit of 1% or 3% or 5% or 7% or 8% or 10% or 12% or 15%or 18% and an upper limit of 20% or 22% or 25% or 30% or 35% or 40% or42% or 50% or 55% or 60% or 66% or 71% or 75% or 80%. In one preferredembodiment, the concentration of plasticizer falls within the range ofabout 7% to about 75%, preferably about 9% to about 55%, and morepreferably about 15% to about 50%.

It is believed that adding the plasticizer to the ethylene acidcopolymer helps make the composition softer and more rubbery. Adding theplasticizers to the composition helps decrease the stiffness of thecomposition. That is, the plasticizer helps lower the flex modulus ofthe composition. The flex modulus refers to the ratio of stress tostrain within the elastic limit (when measured in the flexural mode) andis similar to tensile modulus. This property is used to indicate thebending stiffness of a material. The flexural modulus, which is amodulus of elasticity, is determined by calculating the slope of thelinear portion of the stress-strain curve during the bending test. Ifthe slope of the stress-strain curve is relatively steep, the materialhas a relatively high flexural modulus meaning the material resistsdeformation. The material is more rigid. If the slope is relativelyflat, the material has a relatively low flexural modulus meaning thematerial is more easily deformed. The material is more flexible. Theflex modulus can be determined in accordance with ASTM D790 standardamong other testing procedures. Thus, in one embodiment, the firstethylene acid copolymer (containing ethylene acid copolymer only)composition has a first flex modulus value and the second ethylene acidcopolymer (containing ethylene acid copolymer and plasticizer)composition has a second flex modulus value, wherein the second flexmodulus value is at least 1% less; or at least 2% less; or at least 4%less; or at least 8% less; or at least 10% less than the first modulusvalue.

Plasticized thermoplastic compositions of the present invention are notlimited by any particular method or any particular equipment for makingthe compositions. In a preferred embodiment, the composition is preparedby the following process. The acid copolymer(s), plasticizer, optionalmelt-flow modifier(s), and optional additive(s)/filler(s) aresimultaneously or individually fed into a melt extruder, such as asingle or twin screw extruder. If the acid polymer is to be neutralized,a suitable amount of cation source is then added to achieve the desiredlevel of neutralization neutralized. The acid polymer may be partiallyor fully neutralized prior to the above process. The components areintensively mixed prior to being extruded as a strand from the die-head.Additional methods for incorporating plasticizer into the thermoplasticcompositions herein are disclosed in co-pending U.S. patent applicationSer. No. 13/929,841, as well as in U.S. Pat. Nos. 8,523,708 and8,523,709, which are fully incorporated by reference herein.

More particularly, in one embodiment, the ethylene acidcopolymer/plasticizer composition has a flex modulus lower limit ofabout 500 (or less), 1,000, 1,600, 2,000, 4,200, 7,500, 9,000, 10,000 or20,000 or 40,000 or 50,000 or 60,000 or 70,000 or 80,000 or 90,000 or100,000; and a flex modulus upper limit of about 110,000 or 120,000 or130,000 psi or 140,000 or 160,000 or 180,000 or 200,000 or 300,000 orgreater. In general, the properties of flex modulus and hardness arerelated, whereby flex modulus measures the material's resistance tobending, and hardness measures the material's resistance to indentation.In general, as the flex modulus of the material increases, the hardnessof the material also increases. As discussed above, adding theplasticizer to the ethylene acid copolymer helps reduce the flex modulusof the composition and it also helps reduce hardness to a certaindegree. Thus, in one embodiment, the ethylene acid copolymer/plasticizercomposition is relatively soft and having a hardness of no greater than40 Shore D or no greater than 55 Shore C. For example, the Shore Dhardness may be within a range having a lower limit of 5 or 8 or 10 or12 or 14 and an upper limit of 28 or 30 or 32 or 34 or 35 or 38 or 40Shore D. The Shore C hardness may be within the range having a lowerlimit of 10 or 13 or 15 or 17 or 19 and an upper limit of 44 or 46 or 48or 50 or 53 or 55 Shore C. In other embodiments, the ethylene acidcopolymer/plasticizer composition is moderately soft having a hardnessof no greater than about 60 Shore D or no greater than 75 Shore C. Forexample, the Shore D hardness may be within a range having a lower limitof 25, 28, 20, 32, 35, 36, 38, or 40, and an upper limit of 42, 45, 48,50, 54, 56, or 60. The Shore C hardness may be within the range ofhaving a lower limit of 30, 33, 35, 37, 39, 41, or 43, and an upperlimit of 62, 64, 66, 68, 71, 73 or 75 Shore C. In yet other embodiments,the ethylene acid copolymer/plasticizer composition is moderately hardhaving a hardness no greater than 95 Shore D or no greater than 99 C.For example, the Shore D hardness may be within the range having a lowerlimit of about 42, 44, 47, 51, 53, or 58 and an upper limit of about 60,65, 72, 77, 80, 84, 91, or 95 Shore D. The Shore C hardness may bewithin the range having a lower limit of 57, 59, 62, 66, or 72 and anupper limit of about 75, 78, 84, 87, 90, 93, 95, 97, or 99 Shore C.

It also is believed that adding the plasticizer to the ethylene acidcopolymer composition helps reduce the glass transition temperature (Tg)of the composition in many instances. Thus, in one embodiment, the firstethylene acid copolymer (containing ethylene acid copolymer only)composition has a first Tg value and the second ethylene acid copolymer(containing ethylene acid copolymer and plasticizer) composition has asecond Tg value, wherein the second Tg value is at least 1 degree (1°)less; or at least 2° less; or at least 4° less; or at least 8°; or atleast 10° less than the first Tg value. In other embodiments, the firstTg value and the second Tg value are approximately the same.

In addition, introducing the specific plasticizers of this inventioninto the ethylene acid copolymer composition generally helps to reducethe compression and/or increase the COR of the composition (when moldedinto a solid sphere and tested) versus a non-plasticized composition(when molded into a solid sphere and tested.) Plasticized ethylene acidcopolymer compositions typically show compression values lower, or atmost equal to, non-plasticized compositions while the plasticizedcompositions display COR values that may be higher, or at the leastequal to, non-plasticized compositions. This effect is surprising,because in many conventional compositions, the compression of thecomposition increases as the COR increases. In some instancesplasticization of the composition might produce a slight reduction inthe COR while at the same time reducing the compression to a greaterextent, thereby providing an overall improvement to the compression/CORrelationship over the non-plasticized composition.

More particularly, referring to FIG. 1, the Coefficient of Restitution(CoR) of some sample spheres made of ethylene acid copolymercompositions of this invention are plotted against the DCM Compression(DCM) of the samples. The samples were 1.55″ injection-molded spheresaged two weeks at 23° C./50% RH. In FIG. 1, the “High-PerformanceCommercial HNP Index” (also referred to as “Soft and Fast Index (SFI) inthe Examples/Tables below) is constructed from the properties ofcommercially-available highly neutralized polymers (HNP) with goodresilience-to-hardness and -compression relationships, e.g., HPF AD1035,HPF AD1035Soft, and HPF2000. These ethylene acid copolymers are highlyneutralized (about 90% or greater neutralization levels). In particular,the compositions described in the following Index Table were used toconstruct the Index. In FIG. 1, the plot shows resiliency versuscompression only. But, there are similar relationships betweenresiliency and hardness; and Shore C and Shore D hardness values forvarious samples are reported in the Examples/Tables below.

Index Table Solid Solid Sphere Sphere Solid Sphere Shore D Solid SphereExample COR Compression Hardness Shore C Hardness HPF AD1035 0.822 6341.7 70.0 HPF AD1035 0.782 35 35.6 59.6 Soft HPF 2000 0.856 91 46.1 76.5HPF AD1172 0.785 25 — — HPF 1000 0.831 114 51.5 84.8 HPF AD1035 - acidcopolymer ionomer resin, available from the DuPont Company. HPF AD1035Soft - acid copolymer ionomer resin, available from the DuPont Company.HPF 2000 - acid copolymer ionomer resin, available from the DuPontCompany. HPF AD1172 - acid copolymer ionomer resin, available from theDuPont Company. HPF 1000 - acid copolymer ionomer resin, available fromthe DuPont Company.

As shown in the Index Line of FIG. 1, the CoR of the HPF samplesgenerally decreases as the DCM Compression of the Samples decreases.This relationship between the CoR and Compression in spheres made fromconventional ethylene acid copolymer ionomers, as demonstrated by theIndex, is generally expected. Normally, the resiliency of a balldecreases as the compression of the ball decreases.

Turning to Line A in FIG. 1, the following highly neutralized ethyleneacid copolymer (HNP) compositions are plotted. These ethylene acidcopolymers are highly neutralized (about 90% or greater neutralizationlevels).

TABLE A HPF Compositions Solid Solid Sphere Solid Sphere Sphere SolidSphere Shore D Shore C Example COR Compression Hardness Hardness HPF2000 0.856 91 46.1 76.5 HPF 2000 with 0.839 68 37.9 68.8 10% EO (90/10)HPF 2000 with 0.810 32 30.2 53.0 20% EO (80/20) HPF 2000 with 0.768 −1222.7 39.4 30% EO (70/30) HPF 1000 with 0.846 99 47.2 81.2 10% EO (90/10)EO—ethyl oleate (plasticizer)

As expected, the resiliency of the samples comprising Line A generallydecreases as the compression decreases. However, when comparing Line Ato the Index, there are some interesting and surprising relationships tonote. First, each different embodiment of a plasticized composition ofthis invention (HPF 2000 with EO samples indicated as points on Line A)has a higher absolute CoR versus the corresponding point on the Index ata given compression. (See, for example, the point for Sample HPF 2000with 10% EO versus the corresponding point on the Index). Thus, thesesamples made from plasticized compositions of this invention show agreater absolute resiliency than samples made from conventionalmaterials at a given compression. Having this relatively high resiliencyis an advantageous feature. In general, a core with higher resiliencywill reach a higher velocity when struck by a golf club and travellonger distances. The “feel” of the ball also is important and thisgenerally refers to the sensation that a player experiences whenstriking the ball with the club. The feel of a ball is a difficultproperty to quantify. Most players prefer balls having a soft feel,because the player experience a more natural and comfortable sensationwhen their club face makes contact with these balls. The feel of theball primarily depends upon the hardness and compression of the ball.

Secondly, there is an Index value calculated for each of the samplepoints in Line A. The Index value is calculated by subtracting the CoRvalue of the sample point on Line A from the corresponding point on theIndex Line at a given compression. (The Index value can be a positive ornegative number.) As shown, the Index value increases as the CoR andCompression of the samples decrease (i.e., moving from right to leftalong Line A). For instance the Index value is greater for the HPF 2000with 30% EO sample than the Index values for the HPF2000 with 20% and10% EO samples. The slope of Line A is less than the slope of the Index.Thus, the “drop-off” in CoR for a sample as the Compression decreasesfor the samples in Line A is less than the “drop-off” for the samples inthe Index.

Next, in Line B of FIG. 2, the following ethylene acid copolymer ionomercompositions are plotted. These ethylene acid copolymers are partiallyneutralized (about 40% neutralization levels).

TABLE B Surlyn 9320 Compositions Solid Solid Sphere Solid Sphere SphereSolid Sphere Shore D Shore C Example COR Compression Hardness HardnessSurlyn 9320 0.559 40 37.2 62.1 Surlyn 9320 with 0.620 6 26.3 45.8 10% EO(90/10) Surlyn 9320 with 0.618 −31 24.9 38.4 20% EO (80/20) Surlyn 9320with 0.595 −79 18.7 28.0 30% EO (70/30) Surlyn 9320 is based on acopolymer of ethylene with 23.5% n-butyl acrylate and about 9%methacrylic acid that is about 41% neutralized with a zinc cationsource, available from the DuPont Company. EO—ethyl oleate (plasticizer)

Interestingly, there is an increase in the resiliency of the firstsample point comprising Line B (Surlyn 9320 with 10% EO) versus thecontrol point of Line B (Surlyn 9320) as the compression decreases. And,the resiliency of the first and second sample points (Surlyn 9320 with10% EO and Surlyn 9320 with 20% EO) is approximately the same as thecompression decreases. Although each different embodiment of aplasticized composition of this invention (Surlyn 9320 with EO samplesindicated as points on Line B) has a lower absolute CoR versus thecorresponding point on the Index at a given compression, the Indexvalues for Line B are significant and need to be considered. The Indexvalue is calculated by subtracting the CoR value of the sample point onLine B from the corresponding point on the Index Line at a givencompression. (The Index value can be a positive or negative number.)

Particularly, the Index values along Line B increase as the Compressionof the samples decrease (moving from right to left along the graph.) Forinstance the Index value is greater for the Surlyn with 30% EO samplethan the Index values for the Surlyn with 20% EO and 10% EO samples.Significantly, the Index value for the unmodified Surlyn 9320 sample(non-plasticizer containing) is less than the Index value for the Surlyn9320 with 10% EO sample (plasticizer containing). These greater Indexvalues show the improved properties of the samples of this invention. Amaterial made according to this invention is considered to be improvedif its Index number (value) is greater than the Index number (value) ofthe control material (unmodified state) whether or not the material'sabsolute CoR is greater than the CoR of the control material.

Lastly, in Line C of FIG. 2, the following ethylene acid copolymercompositions are plotted. These ethylene acid copolymers arenon-neutralized (0% neutralization levels).

TABLE C Nucrel 9-1 Compositions Solid Solid Sphere Solid Sphere SphereSolid Sphere Shore D Shore C Example COR Compression Hardness HardnessNucrel 9-1 0.449 −37 23.2 40.3 Nucrel 9-1 with 0.501 −67 19.1 26.3 10%EO (90/10) Nucrel 9-1: is a copolymer of ethylene with 23.5% n-butylacrylate, and about 9% methacrylic acid that is non-neutralized,available from the DuPont Company. EO—ethyl oleate (plasticizer)

Like the plotted compositions in Line B, there is an increase in theresiliency of the first sample point comprising Line C (Nucrel 9-1 with10% EO) versus the control point of Line C (Nucrel 9-1) as thecompression decreases. Also, the Nucrel 9-1 with 10% EO sample has alower absolute CoR versus the corresponding point on the Index at agiven compression. However, similar to the Index values of Line B, theIndex values along Line C increase as the compression of the samplesdecrease (moving from right to left along the graph.) The Index value iscalculated by subtracting the CoR value of the sample point on Line Cfrom the corresponding point on the Index Line at a given compression.(The Index value can be a positive or negative number.)

These greater Index values show the improved properties of the samplesof this invention. As discussed above, a material made according to thisinvention is considered to have been improved if its Index number(value) is greater than the Index number (value) of the control material(unmodified state) whether or not the material's absolute CoR hasincreased over the CoR of the control material.

As demonstrated by the plot in FIG. 1, the addition of a fatty acidester plasticizer (ethyl oleate) to an acid copolymer or ionomer, makesthat polymer faster (i.e., higher CoR) at a given compression (or agiven hardness) versus the polymer without plasticizer. This allows thecreation of materials that are faster and softer thancommercially-available polymers. This is very important for golf balllayers, where ball speed (i.e., CoR) is needed for distance, but wherefeel (softness or low compression) is also highly desirable to mostgolfers. The ability to make a softer, better feeling golf ball that hashigher CoR than predicted is surprising and highly beneficial.

Referring to FIG. 3, the Soft and Fast Index (SFI) values for theplasticized thermoplastic compositions shown in FIGS. 1 and 2(plasticized HPF 2000, Surlyn 9320, and Nucrel 9-1) are plotted againstthe concentration (weight percent) of plasticizer in the composition. Asdemonstrated by the plot in FIG. 3, the SFI values increase for each ofthe sample compositions as the concentration of plasticizer increases.The benefits of having high SFI values are discussed above. Theplasticized thermoplastic compositions of this invention can be used tomake cores having an optimum combination of properties including highresiliency and a soft and comfortable feel.

Cover Structure

The golf ball cores of this invention may be enclosed with one or morecover layers. For example, a golf ball having inner and outer coverlayers may be made. In another version, a three-layered cover comprisinginner, intermediate, and outer cover layers may be made. Themulti-layered cover of the golf balls of this invention provide the ballwith a variety of advantageous mechanical and playing performanceproperties as discussed further below. In general, the hardness andthickness of the different cover layers may vary depending upon thedesired ball construction. In addition, as discussed above, anintermediate layer may be disposed between the core and cover layers.The cover layers preferably have good impact durability, toughness, andwear-resistance. The ethylene acid copolymer/plasticizer compositions ofthis invention may be used to form at least one of the cover layers.

In one version, the golf ball includes a multi-layered cover comprisinginner and outer cover layers. The inner cover layer may be formed from acomposition comprising an ionomer or a blend of two or more ionomersthat helps impart hardness to the ball. In a particular embodiment, theinner cover layer is formed from a composition comprising a high acidionomer. A particularly suitable high acid ionomer is Surlyn 8150®(DuPont). Surlyn 8150® is a copolymer of ethylene and methacrylic acid,having an acid content of 19 wt %, which is 45% neutralized with sodium.In another particular embodiment, the inner cover layer is formed from acomposition comprising a high acid ionomer and a maleicanhydride-grafted non-ionomeric polymer. A particularly suitable maleicanhydride-grafted polymer is Fusabond 525D® (DuPont). Fusabond 525D® isa maleic anhydride-grafted, metallocene-catalyzed ethylene-butenecopolymer having about 0.9 wt % maleic anhydride grafted onto thecopolymer. A particularly preferred blend of high acid ionomer andmaleic anhydride-grafted polymer is an 84 wt %/16 wt % blend of Surlyn8150® and Fusabond 525D®. Blends of high acid ionomers with maleicanhydride-grafted polymers are further disclosed, for example, in U.S.Pat. Nos. 6,992,135 and 6,677,401, the entire disclosures of which arehereby incorporated herein by reference.

The inner cover layer also may be formed from a composition comprising a50/45/5 blend of Surlyn® 8940/Surlyn® 9650/Nucrel® 960, and, in aparticularly preferred embodiment, the composition has a materialhardness of from 80 to 85 Shore C. In yet another version, the innercover layer is formed from a composition comprising a 50/25/25 blend ofSurlyn® 8940/Surlyn® 9650/Surlyn® 9910, preferably having a materialhardness of about 90 Shore C. The inner cover layer also may be formedfrom a composition comprising a 50/50 blend of Surlyn® 8940/Surlyn®9650, preferably having a material hardness of about 86 Shore C. Acomposition comprising a 50/50 blend of Surlyn® 8940 and Surlyn® 7940also may be used. Surlyn® 8940 is an E/MAA copolymer in which the MAAacid groups have been partially neutralized with sodium ions. Surlyn®9650 and Surlyn® 9910 are two different grades of E/MAA copolymer inwhich the MAA acid groups have been partially neutralized with zincions. Nucrel® 960 is an E/MAA copolymer resin nominally made with 15 wt% methacrylic acid.

When the inner cover layer is formed from one of the above-describedionomer or other compositions, the outer cover is preferably formed ofthe plasticized thermoplastic composition of this invention as describedabove.

In another version, the inner cover layer is formed from the plasticizedthermoplastic composition of this invention, and the outer cover layeris formed from a suitable thermoset or thermoplastic composition. Insuch instances, suitable materials that can be used to form the outercover layer include, for example, polyurethanes; polyureas; copolymers,blends and hybrids of polyurethane and polyurea; olefin-based copolymerionomer resins (for example, Surlyn® ionomer resins and DuPont HPF®1000, HPF® 2000, and HPF® 1035; and HPF® AD 1172, commercially availablefrom DuPont; Iotek® ionomers, commercially available from ExxonMobilChemical Company; Amplify® 10 ionomers of ethylene acrylic acidcopolymers, commercially available from The Dow Chemical Company; andClarix® ionomer resins, commercially available from A. Schulman Inc.);polyethylene, including, for example, low density polyethylene, linearlow density polyethylene, and high density polyethylene; polypropylene;rubber-toughened olefin polymers; acid copolymers, for example,poly(meth)acrylic acid, which do not become part of an ionomericcopolymer; plastomers; flexomers; styrene/butadiene/styrene blockcopolymers; styrene/ethylene-butylene/styrene block copolymers;dynamically vulcanized elastomers; copolymers of ethylene and vinylacetates; copolymers of ethylene and methyl acrylates; polyvinylchloride resins; polyamides, poly(amide-ester) elastomers, and graftcopolymers of ionomer and polyamide including, for example, Pebax®thermoplastic polyether block amides, commercially available from ArkemaInc; cross-linked trans-polyisoprene and blends thereof; polyester-basedthermoplastic elastomers, such as Hytrel®, commercially available fromDuPont or RiteFlex®, commercially available from Ticona EngineeringPolymers; polyurethane-based thermoplastic elastomers, such asElastollan®, commercially available from BASF; synthetic or naturalvulcanized rubber; and combinations thereof. Castable polyurethanes,polyureas, and hybrids of polyurethanes-polyureas are particularlydesirable because these materials can be used to make a golf ball havinghigh resiliency and a soft feel. By the term, “hybrids of polyurethaneand polyurea,” it is meant to include copolymers and blends thereof.

Polyurethanes, polyureas, and blends, copolymers, and hybrids ofpolyurethane/polyurea are also particularly suitable. When used as theouter cover layer material, polyurethanes and polyureas can be thermosetor thermoplastic. Thermoset materials can be formed into golf balllayers by conventional casting or reaction injection molding techniques.Thermoplastic materials can be formed into golf ball layers byconventional compression or injection molding techniques.

In one particularly preferred version, a two-layered cover is made. Forexample, a cover assembly having inner and outer cover layers, wherein arelatively hard cover is disposed about a relatively soft cover may bemade. Alternatively, a relatively soft cover may be disposed about arelatively hard cover. The ethylene acid copolymer/plasticizercompositions of this invention may be used to form at least one of thecover layers. Other thermoplastic or thermoset compositions as describedabove may be used to form the other cover layer in the two-layered coverassembly. Suitable hardness ranges for the inner and outer cover layersare described below.

In another particularly preferred version, a three-layered cover ismade. For example, a cover assembly having inner and outer cover layers,wherein an intermediate cover layer is disposed between the inner andouter cover layers, may be prepared. In such a construction, theethylene acid copolymer/plasticizer compositions of this invention maybe used to form at least one of the inner, intermediate, or outer coverlayers.

In one version, the inner cover layer hardness is about 15 Shore D orgreater, more preferably about 25 Shore D or greater, and mostpreferably about 35 Shore D or greater. For example, the inner coverlayer hardness may be in the range of about 15 to about 60 Shore D, andmore preferably about 27 to about 48 Shore D. In another version, theinner cover layer hardness is about 50 Shore D or greater, preferablyabout 55 Shore D or greater, and most preferably about 60 Shore D orgreater. For example, in one version, the inner cover has a Shore Dhardness of about 55 to about 90 Shore D. In another embodiment, theinner cover has a Shore D hardness of about 60 to about 78 Shore D, andin yet another version, the inner cover has a Shore D hardness of about64 to about 72 Shore D. More particularly, in one example, the innercover has a hardness of about 65 Shore D or greater. The hardness of theinner cover layer is measured per the methods described further below.In addition, the thickness of the inner cover layer is preferably about0.015 inches to about 0.100 inches, more preferably about 0.020 inchesto about 0.080 inches, and most preferably about 0.030 inches to about0.050 inches. Typically, the thickness of the inner cover is about 0.035or 0.040 or 0.045 inches.

In one version, the intermediate cover layer preferably has a materialhardness of 70 Shore D or less, or 65 Shore D or less, or 60 Shore D orless, or 55 Shore D or less. Preferably, the intermediate cover has aShore D hardness in the range of about 25 Shore D to about 60 Shore D,more preferably about 38 to about 50 Shore D. In other embodiments,however, the intermediate cover has a hardness of greater than 70 ShoreD, for example, 75 Shore D or greater. Also, the thickness of theintermediate cover layer is preferably about equal to or greater thanthe thickness of the outer cover layer. More particularly, the thicknessof the inner cover layer is preferably about 0.005 inches to about 0.040inches, more preferably about 0.010 inches to about 0.035 inches, andmost preferably about 0.015 inches to 0.030 inches.

Concerning the outer cover layer, this layer may be relatively thin. Theouter cover preferably has a thickness within a range having a lowerlimit of 0.004 or 0.006 or 0.008 and an upper limit of 0.010 or 0.020 or0.030 or 0.040 inches. Preferably, the thickness of the outer cover isabout 0.016 inches or less, more preferably 0.008 inches or less. Theouter cover preferably has a material hardness of 80 Shore D or less, or70 Shore D or less, or 60 Shore D or less, or 55 Shore D or less, or 50Shore D or less, or 45 Shore D or less. In one example, the outer coverpreferably has a Shore D hardness in the range of about 50 to about 80,more preferably about 55 to about 75. In another example, the outercover preferably has a Shore D hardness in the range of about 10 toabout 70, more preferably about 15 to about 60. The hardness of theouter cover layer is measured per the methods described further below.

The hardness of a cover layer may be measured on the surface or midpointof the given layer in a manner similar to measuring the hardness of acore layer as described further below. For example, the hardness of theinner cover layer may be measured at the surface or midpoint of thelayer. A midpoint hardness measurement is preferably made for the innerand intermediate cover layers. The midpoint hardness of a cover layer istaken at a point equidistant from the inner surface and outer surface ofthe layer to be measured. Once one or more cover or other ball layerssurround a layer of interest, the exact midpoint may be difficult todetermine, therefore, for the purposes of the present invention, themeasurement of “midpoint” hardness of a layer is taken within plus orminus 1 mm of the measured midpoint of the layer. A surface hardnessmeasurement is preferably made for the outer cover layer. In theseinstances, the hardness is measured on the outer surface (cover) of theball. Methods for measuring the hardness are described in detail belowunder “Test Methods.”

The relationship between the various cover layers is important in theconstruction of the golf ball of this invention. For example, in oneembodiment, the plasticized thermoplastic composition of this inventionis used to form the intermediate cover layer, and the hardness of theinner cover is greater than the hardness of the intermediate coverlayer, preferably by at least 5 Shore D units. Meanwhile, the outercover layer hardness is greater than the intermediate cover layerhardness, preferably by at least 5 Shore D Units.

In a second embodiment, the plasticized thermoplastic composition isused to form the intermediate cover layer, and the hardness of the innercover and intermediate cover layers is substantially the same. In thisembodiment, both the inner cover and intermediate covers have a hardnessthat is greater than the outer cover layer hardness, preferably by atleast 5 Shore D Units.

In a third embodiment, the inner cover layer hardness is greater thanthe intermediate (plasticized thermoplastic composition) and outer coverlayer hardness, preferably by at least 5 Shore D units. In thisembodiment, the intermediate and outer cover layers may havesubstantially the same hardness.

In a fourth embodiment, the plasticized thermoplastic composition isused to form the intermediate cover layer, and the hardness of the innercover is less than the hardness of the intermediate cover layer,preferably by at least 5 Shore D units. Also, the intermediate coverlayer hardness is greater than the outer cover layer hardness preferablyby at least 5 Shore D Units.

In a fifth embodiment, the plasticized thermoplastic composition is usedto form the intermediate cover layer, and the hardness of the innercover and intermediate cover layers is substantially the same. Both theinner cover and intermediate covers have a hardness that is less thanthe outer cover layer hardness in this embodiment.

In a sixth embodiment, the inner cover layer hardness is less than theintermediate (plasticized thermoplastic composition) and outer coverlayer hardness, preferably by at least 5 Shore D units. The intermediateand outer cover layers may have substantially the same hardness in thisembodiment.

The compositions used to make any cover layer (for example, inner,intermediate, or outer cover layer) may contain a wide variety offillers and additives to impart specific properties to the ball. Forexample, relatively heavy-weight and light-weight metal fillers such as,particulate; powders; flakes; and fibers of copper, steel, brass,tungsten, titanium, aluminum, magnesium, molybdenum, cobalt, nickel,iron, lead, tin, zinc, barium, bismuth, bronze, silver, gold, andplatinum, and alloys and combinations thereof may be used to adjust thespecific gravity of the ball. Other additives and fillers include, butare not limited to, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, surfactants,processing aids, antioxidants, stabilizers, softening agents, fragrancecomponents, plasticizers, impact modifiers, titanium dioxide, clay,mica, talc, glass flakes, milled glass, and mixtures thereof.

In an alternative version of a three-layered cover, the plasticizedthermoplastic composition of this invention is used to form the innercover layer. In yet another version, the plasticized thermoplasticcomposition is used to form the outer cover layer. Suitable thermosetand other thermoplastic compositions as described above may be used toform the other cover layers. The plasticized thermoplastic compositionof this invention may be used to form one or more cover layers inaccordance with this invention.

The different hardness and thickness levels of the cover layers providethe ball with high impact durability and cut-, shear- andtear-resistance levels. In addition, the multi-layered cover, incombination with the core layer, helps impart high resiliency to thegolf balls. Preferably, the golf ball has a Coefficient of Restitution(CoR) of at least 0.750 and more preferably at least 0.800 (as measuredper the test methods below.) The core of the golf ball generally has acompression in the range of about 50 to about 130 and more preferably inthe range of about 70 to about 110 (as measured per the test methodsbelow.) These properties allow players to generate greater ball velocityoff the tee and achieve greater distance with their drives. At the sametime, the cover layers provide a player with a more comfortable andnatural feeling when striking the ball with a club. The ball is moreplayable and the ball's flight path can be controlled more easily.

Referring to FIG. 4, a two-piece golf ball (4) comprising an inner core(center) (6) and an outer cover layer (8) is shown. Preferably, theouter cover comprises a plasticized thermoplastic composition of thisinvention. In another embodiment, a three-piece golf ball (10) is made,wherein the core (11) is surrounded by a two-layered cover (12)comprising an inner cover layer (14) and outer cover layer (16), may bemade as shown in FIG. 5. A four-piece ball also can be made as shown inFIG. 6, wherein ball (18) contains a dual-core having an inner core (20)and outer core layer (22). The dual-core is surrounded by amulti-layered cover having an inner cover layer (24) and outer coverlayer (26). Referring to FIG. 7, in another version, the four-piece golfball (30) contains a multi-layered cover comprising inner cover layer(32 a), intermediate cover layer (32 b), and outer cover layer (32 c)surrounding a solid, one-piece core (33). Turning to FIG. 8, thefive-piece ball (36) includes a dual-core (38) comprising an inner core(center) (38 a) and surrounding outer core layer (38 b). Themulti-layered cover (40) encapsulates the core structure (38) andincludes inner (40 a), intermediate (40 b), and outer (40 c) coverlayers.

Different ball constructions can be made using the cover assembly ofthis invention as shown in FIGS. 4-8 discussed above. Such golf ballconstructions include, for example, two-piece, three-piece, four-piece,five-piece, and six-piece constructions. It should be understood thatthe golf balls shown in FIGS. 4-8 are for illustrative purposes only,and they are not meant to be restrictive. Other golf ball constructionscan be made in accordance with this invention.

Core Structure

The cover layers described above are disposed about a core assembly.Single-layer or multi-layer cores may be made. For example, atwo-layered core having an inner core (center) and surrounding outercore layer may be made in accordance with this invention. In anotherexample, a three-layered core having an inner core and outer core layer,wherein an intermediate core layer is disposed between the inner andouter core layers may be made. The plasticized thermoplasticcompositions, which are described above as being suitable for makingcover layers, are also suitable for forming the core layers. Thermosetrubber compositions and non-plasticized thermoplastic compositions alsoare suitable for making core layers in accordance with this invention

In one preferred embodiment, the inner core (center) comprises athermoplastic material and more preferably the plasticized thermoplasticmaterial of this invention. In general, the plasticized thermoplasticcomposition comprises: a) an acid copolymer of ethylene and anα,β-unsaturated carboxylic acid, optionally including a softeningmonomer selected from the group consisting of alkyl acrylates andmethacrylates; and b) a plasticizer. In one preferred embodiment, acation source is present in an amount sufficient to neutralize greaterthan 20% of all acid groups present in the composition. The compositionmay comprise a highly-neutralized polymer (HNP); partially-neutralizedacid polymer; or lowly-neutralized or non-neutralized acid polymer, andblends thereof as described above. Suitable plasticizers that may beused to plasticize the thermoplastic compositions are also describedabove.

In another embodiment, the inner core comprises a thermoset material.Suitable thermoset materials that may be used to form the inner coreinclude, but are not limited to, polybutadiene, polyisoprene, ethylenepropylene rubber (“EPR”), ethylene-propylene-diene (“EPDM”) rubber,styrene-butadiene rubber, styrenic block copolymer rubbers (such as“SI”, “SIS”, “SB”, “SBS”, “SIBS”, and the like, where “S” is styrene,“I” is isobutylene, and “B” is butadiene), polyalkenamers such as, forexample, polyoctenamer, butyl rubber, halobutyl rubber, polystyreneelastomers, polyethylene elastomers, polyurethane elastomers, polyureaelastomers, metallocene-catalyzed elastomers and plastomers, copolymersof isobutylene and p-alkylstyrene, halogenated copolymers of isobutyleneand p-alkylstyrene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber,acrylonitrile chlorinated isoprene rubber, and blends of two or morethereof.

The thermoset rubber materials may be cured using a conventional curingprocess as described further below. Suitable curing processes include,for example, peroxide-curing, sulfur-curing, high-energy radiation, andcombinations thereof. Preferably, the rubber composition contains afree-radical initiator selected from organic peroxides, high energyradiation sources capable of generating free-radicals, and combinationsthereof.

Suitable thermoset rubber materials that may be used to form the corelayers include, but are not limited to, polybutadiene, polyisoprene,ethylene propylene rubber (“EPR”), ethylene-propylene-diene (“EPDM”)rubber, styrene-butadiene rubber, styrenic block copolymer rubbers (suchas “SI”, “SIS”, “SB”, “SBS”, “SIBS”, and the like, where “S ” isstyrene, “I” is isobutylene, and “B” is butadiene), polyalkenamers suchas, for example, polyoctenamer, butyl rubber, halobutyl rubber,polystyrene elastomers, polyethylene elastomers, polyurethaneelastomers, polyurea elastomers, metallocene-catalyzed elastomers andplastomers, copolymers of isobutylene and p-alkylstyrene, halogenatedcopolymers of isobutylene and p-alkylstyrene, copolymers of butadienewith acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinatedisoprene rubber, acrylonitrile chlorinated isoprene rubber, and blendsof two or more thereof. Preferably, the outer core layer is formed froma polybutadiene rubber composition.

The thermoset rubber composition may be cured using conventional curingprocesses. Suitable curing processes include, for example,peroxide-curing, sulfur-curing, high-energy radiation, and combinationsthereof. Preferably, the rubber composition contains a free-radicalinitiator selected from organic peroxides, high energy radiation sourcescapable of generating free-radicals, and combinations thereof. In onepreferred version, the rubber composition is peroxide-cured. Suitableorganic peroxides include, but are not limited to, dicumyl peroxide;n-butyl-4,4-di(t-butylperoxy) valerate;1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide;di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoylperoxide; t-butyl hydroperoxide; and combinations thereof. In aparticular embodiment, the free radical initiator is dicumyl peroxide,including, but not limited to Perkadox BC, commercially available fromAkzo Nobel. Peroxide free-radical initiators are generally present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the total rubber, or an amount within the range having alower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5parts or 2.5 parts or 5 parts by weight per 100 parts of the totalrubbers, and an upper limit of 2.5 parts or 3 parts or 5 parts or 6parts or 10 parts or 15 parts by weight per 100 parts of the totalrubber. Concentrations are in parts per hundred (phr) unless otherwiseindicated. As used herein, the term, “parts per hundred,” also known as“phr” or “pph” is defined as the number of parts by weight of aparticular component present in a mixture, relative to 100 parts byweight of the polymer component. Mathematically, this can be expressedas the weight of an ingredient divided by the total weight of thepolymer, multiplied by a factor of 100.

The rubber compositions may further include a reactive cross-linkingco-agent. Suitable co-agents include, but are not limited to, metalsalts of unsaturated carboxylic acids having from 3 to 8 carbon atoms;unsaturated vinyl compounds and polyfunctional monomers (e.g.,trimethylolpropane trimethacrylate); phenylene bismaleimide; andcombinations thereof. Particular examples of suitable metal saltsinclude, but are not limited to, one or more metal salts of acrylates,diacrylates, methacrylates, and dimethacrylates, wherein the metal isselected from magnesium, calcium, zinc, aluminum, lithium, and nickel.In a particular embodiment, the co-agent is selected from zinc salts ofacrylates, diacrylates, methacrylates, and dimethacrylates. In anotherparticular embodiment, the agent is zinc diacrylate (ZDA). When theco-agent is zinc diacrylate and/or zinc dimethacrylate, the co-agent istypically included in the rubber composition in an amount within therange having a lower limit of 1 or 5 or 10 or 15 or 19 or 20 parts byweight per 100 parts of the total rubber, and an upper limit of 24 or 25or 30 or 35 or 40 or 45 or 50 or 60 parts by weight per 100 parts of thebase rubber.

Radical scavengers such as a halogenated organosulfur, organicdisulfide, or inorganic disulfide compounds may be added to the rubbercomposition. These compounds also may function as “soft and fastagents.” As used herein, “soft and fast agent” means any compound or ablend thereof that is capable of making a core: 1) softer (having alower compression) at a constant “coefficient of restitution” (COR);and/or 2) faster (having a higher COR at equal compression), whencompared to a core equivalently prepared without a soft and fast agent.Preferred halogenated organosulfur compounds include, but are notlimited to, pentachlorothiophenol (PCTP) and salts of PCTP such as zincpentachlorothiophenol (ZnPCTP). Using PCTP and ZnPCTP in golf ball innercores helps produce softer and faster inner cores. The PCTP and ZnPCTPcompounds help increase the resiliency and the coefficient ofrestitution of the core. In a particular embodiment, the soft and fastagent is selected from ZnPCTP, PCTP, ditolyl disulfide, diphenyldisulfide, dixylyl disulfide, 2-nitroresorcinol, and combinationsthereof.

The rubber composition also may include filler(s) such as materialsselected from carbon black, nanoclays (e.g., Cloisite® and Nanofil®nanoclays, commercially available from Southern Clay Products, Inc., andNanomax® and Nanomer® nanoclays, commercially available from Nanocor,Inc.), talc (e.g., Luzenac HAR® high aspect ratio talcs, commerciallyavailable from Luzenac America, Inc.), glass (e.g., glass flake, milledglass, and microglass), mica and mica-based pigments (e.g., Iriodin®pearl luster pigments, commercially available from The Merck Group), andcombinations thereof. Metal fillers such as, for example, particulate;powders; flakes; and fibers of copper, steel, brass, tungsten, titanium,aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc,barium, bismuth, bronze, silver, gold, and platinum, and alloys andcombinations thereof also may be added to the rubber composition toadjust the specific gravity of the composition as needed.

In addition, the rubber compositions may include antioxidants to preventthe breakdown of the elastomers. Also, processing aids such as highmolecular weight organic acids and salts thereof may be added to thecomposition. Suitable organic acids are aliphatic organic acids,aromatic organic acids, saturated mono-functional organic acids,unsaturated monofunctional organic acids, multi-unsaturatedmono-functional organic acids, and dimerized derivatives thereof.Particular examples of suitable organic acids include, but are notlimited to, caproic acid, caprylic acid, capric acid, lauric acid,stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid,myristic acid, benzoic acid, palmitic acid, phenylacetic acid,naphthalenoic acid, and dimerized derivatives thereof. The organic acidsare aliphatic, mono-functional (saturated, unsaturated, ormulti-unsaturated) organic acids. Salts of these organic acids may alsobe employed. The salts of organic acids include the salts of barium,lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium,strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver,aluminum, tin, or calcium, salts of fatty acids, particularly stearic,behenic, erucic, oleic, linoelic or dimerized derivatives thereof. It ispreferred that the organic acids and salts of the present invention berelatively non-migratory (they do not bloom to the surface of thepolymer under ambient temperatures) and non-volatile (they do notvolatilize at temperatures required for melt-blending.) Otheringredients such as accelerators (for example, tetra methylthiuram),processing aids, dyes and pigments, wetting agents, surfactants,plasticizers, coloring agents, fluorescent agents, chemical blowing andfoaming agents, defoaming agents, stabilizers, softening agents, impactmodifiers, antiozonants, as well as other additives known in the art maybe added to the rubber composition.

Examples of commercially-available polybutadiene rubbers that can beused in accordance with this invention, include, but are not limited to,BR 01 and BR 1220, available from BST Elastomers of Bangkok, Thailand;SE BR 1220LA and SE BR1203, available from DOW Chemical Co of Midland,Mich.; BUDENE 1207, 1207s, 1208, and 1280 available from Goodyear, Incof Akron, Ohio; BR 01, 51 and 730, available from Japan Synthetic Rubber(JSR) of Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29MES, CB 60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221,available from Lanxess Corp. of Pittsburgh. Pa.; BR1208, available fromLG Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B, BR150L,BR230, BR360L, BR710, and VCR617, available from UBE Industries, Ltd. ofTokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60 AF and P30AF, andEUROPRENE BR HV80, available from Polimeri Europa of Rome, Italy; AFDENE50 and NEODENE BR40, BR45, BR50 and BR60, available from Karbochem (PTY)Ltd. of Bruma, South Africa; KBR 01, NdBr 40, NdBR-45, NdBr 60, KBR710S, KBR 710H, and KBR 750, available from Kumho Petrochemical Co.,Ltd. Of Seoul, South Korea; DIENE 55NF, 70AC, and 320 AC, available fromFirestone Polymers of Akron, Ohio.

The polybutadiene rubber is used in an amount of at least about 5% byweight based on total weight of composition and is generally present inan amount of about 5% to about 100%, or an amount within a range havinga lower limit of 5% or 10% or 20% or 30% or 40% or 50% and an upperlimit of 55% or 60% or 70% or 80% or 90% or 95% or 100%. Preferably, theconcentration of polybutadiene rubber is about 40 to about 95 weightpercent. If desirable, lesser amounts of other thermoset materials maybe incorporated into the base rubber. Such materials include the rubbersdiscussed above, for example, cis-polyisoprene, trans-polyisoprene,balata, polychloroprene, polynorbornene, polyoctenamer, polypentenamer,butyl rubber, EPR, EPDM, styrene-butadiene, and the like.

As discussed above, in one embodiment, the core has a dual-layeredstructure. For example, an inner core (center) comprising athermoplastic ethylene acid copolymer or thermoset rubber composition asdescribed above may be prepared. Meanwhile, the outer core layer, whichsurrounds the inner core, also may comprise a thermoplastic or thermosetcomposition. In another embodiment, the core has a three-layeredstructure comprising an inner core, intermediate core layer, and outercore layer. For example, the core may include an an inner corecomprising the plasticized thermoplastic composition of this invention;an intermediate core layer comprising a thermoplastic composition; andan outer core layer comprising a thermoset rubber composition.

Hardness of Core

The hardness of the core assembly (inner core and outer core layer) isan important property. In general, cores with relatively high hardnessvalues have higher compression and tend to have good durability andresiliency. However, some high compression balls are stiff and this mayhave a detrimental effect on shot control and placement. Thus, theoptimum balance of hardness in the core assembly needs to be attained.

In one preferred golf ball, the inner core (center) has a “positive”hardness gradient (that is, the outer surface of the inner core isharder than its geometric center); and the outer core layer has a“positive” hardness gradient (that is, the outer surface of the outercore layer is harder than the inner surface of the outer core layer.) Insuch cases where both the inner core and outer core layer each has a“positive” hardness gradient, the outer surface hardness of the outercore layer is preferably greater than the hardness of the geometriccenter of the inner core. In one preferred version, the positivehardness gradient of the inner core is in the range of about 2 to about40 Shore C units and even more preferably about 10 to about 25 Shore Cunits; while the positive hardness gradient of the outer core is in therange of about 2 to about 20 Shore C and even more preferably about 3 toabout 10 Shore C.

In an alternative version, the inner core may have a positive hardnessgradient; and the outer core layer may have a “zero” hardness gradient(that is, the hardness values of the outer surface of the outer corelayer and the inner surface of the outer core layer are substantiallythe same) or a “negative” hardness gradient (that is, the outer surfaceof the outer core layer is softer than the inner surface of the outercore layer.) For example, in one version, the inner core has a positivehardness gradient; and the outer core layer has a negative hardnessgradient in the range of about 2 to about 25 Shore C. In a secondalternative version, the inner core may have a zero or negative hardnessgradient; and the outer core layer may have a positive hardnessgradient. Still yet, in another embodiment, both the inner core andouter core layers have zero or negative hardness gradients.

In general, hardness gradients are further described in Bulpett et al.,U.S. Pat. Nos. 7,537,529 and 7,410,429, the disclosures of which arehereby incorporated by reference. Methods for measuring the hardness ofthe inner core and outer core layers along with other layers in the golfball and determining the hardness gradients of the various layers aredescribed in further detail below. The core layers have positive,negative, or zero hardness gradients defined by hardness measurementsmade at the outer surface of the inner core (or outer surface of theouter core layer) and radially inward towards the center of the innercore (or inner surface of the outer core layer). These measurements aremade typically at 2-mm increments as described in the test methodsbelow. In general, the hardness gradient is determined by subtractingthe hardness value at the innermost portion of the component beingmeasured (for example, the center of the inner core or inner surface ofthe outer core layer) from the hardness value at the outer surface ofthe component being measured (for example, the outer surface of theinner core or outer surface of the outer core layer).

Positive Hardness Gradient. For example, if the hardness value of theouter surface of the inner core is greater than the hardness value ofthe inner core's geometric center (that is, the inner core has a surfaceharder than its geometric center), the hardness gradient will be deemed“positive” (a larger number minus a smaller number equals a positivenumber.) For example, if the outer surface of the inner core has ahardness of 67 Shore C and the geometric center of the inner core has ahardness of 60 Shore C, then the inner core has a positive hardnessgradient of 7. Likewise, if the outer surface of the outer core layerhas a greater hardness value than the inner surface of the outer corelayer, the given outer core layer will be considered to have a positivehardness gradient.

Negative Hardness Gradient. On the other hand, if the hardness value ofthe outer surface of the inner core is less than the hardness value ofthe inner core's geometric center (that is, the inner core has a surfacesofter than its geometric center), the hardness gradient will be deemed“negative.” For example, if the outer surface of the inner core has ahardness of 68 Shore C and the geometric center of the inner core has ahardness of 70 Shore C, then the inner core has a negative hardnessgradient of 2. Likewise, if the outer surface of the outer core layerhas a lesser hardness value than the inner surface of the outer corelayer, the given outer core layer will be considered to have a negativehardness gradient.

Zero Hardness Gradient. In another example, if the hardness value of theouter surface of the inner core is substantially the same as thehardness value of the inner core's geometric center (that is, thesurface of the inner core has about the same hardness as the geometriccenter), the hardness gradient will be deemed “zero.” For example, ifthe outer surface of the inner core and the geometric center of theinner core each has a hardness of 65 Shore C, then the inner core has azero hardness gradient. Likewise, if the outer surface of the outer corelayer has a hardness value approximately the same as the inner surfaceof the outer core layer, the outer core layer will be considered to havea zero hardness gradient.

More particularly, the term, “positive hardness gradient” as used hereinmeans a hardness gradient of positive 3 Shore C or greater, preferably 7Shore C or greater, more preferably 10 Shore C, and even more preferably20 Shore C or greater. The term, “zero hardness gradient” as used hereinmeans a hardness gradient of less than 3 Shore C, preferably less than 1Shore C and may have a value of zero or negative 1 to negative 10 ShoreC. The term, “negative hardness gradient” as used herein means ahardness value of less than zero, for example, negative 3, negative 5,negative 7, negative 10, negative 15, or negative 20 or negative 25. Theterms, “zero hardness gradient” and “negative hardness gradient” may beused herein interchangeably to refer to hardness gradients of negative 1to negative 10.

The inner core preferably has a geometric center hardness(H_(inner core center)) of about 5 Shore D or greater. For example, the(H_(inner core center)) may be in the range of about 5 to about 88 ShoreD and more particularly within a range having a lower limit of about 5or 10 or 18 or 20 or 26 or 30 or 34 or 36 or 38 or 42 or 48 or 50 or 52Shore D and an upper limit of about 54 or 56 or 58 or 60 or 62 or 64 or68 or 70 or 74 or 76 or 80 or 82 or 84 or 88 Shore D. In anotherexample, the center hardness of the inner core (H_(inner core center)),as measured in Shore C units, is preferably about 10 Shore C or greater;for example, the H_(inner core center) may have a lower limit of about10 or 14 or 16 or 20 or 23 or 24 or 28 or 31 or 34 or 37 or 40 or 44Shore C and an upper limit of about 46 or 48 or 50 or 51 or 53 or 55 or58 or 61 or 62 or 65 or 68 or 71 or 74 or 76 or 78 or 79 or 80 or 84 or90 Shore C. Concerning the outer surface hardness of the inner core(H_(inner core surface)), this hardness is preferably about 12 Shore Dor greater; for example, the H_(inner core surface) may fall within arange having a lower limit of about 12 or 15 or 18 or 20 or 22 or 26 or30 or 34 or 36 or 38 or 42 or 48 or 50 or 52 Shore D and an upper limitof about 54 or 56 or 58 or 60 or 62 or 70 or 72 or 75 or 78 or 80 or 82or 84 or 86 or 90 Shore D. In one version, the outer surface hardness ofthe inner core (H_(inner core surface)), as measured in Shore C units,has a lower limit of about 13 or 15 or 18 or 20 or 22 or 24 or 27 or 28or 30 or 32 or 34 or 38 or 44 or 47 or 48 Shore C and an upper limit ofabout 50 or 54 or 56 or 61 or 65 or 66 or 68 or 70 or 73 or 76 or 78 or80 or 84 or 86 or 88 or 90 or 92 Shore C. In another version, thegeometric center hardness (H_(inner core center)) is in the range ofabout 10 Shore C to about 50 Shore C; and the outer surface hardness ofthe inner core (H_(inner core surface)) is in the range of about 5 ShoreC to about 50 Shore C.

Meanwhile, the intermediate core layer preferably has an outer surfacehardness (H_(outer surface of the Inter Core)) of about 30 Shore D orgreater, and more preferably within a range having a lower limit ofabout 30 or 35 or 40 or 42 or 44 or 46 or 48 or 50 or 52 or 54 or 56 or58 and an upper limit of about 60 or 62 or 64 or 70 or 74 or 78 or 80 or82 or 85 or 87 or 88 or 90 Shore D. The outer surface hardness of theintermediate core layer (H_(outer surface of the Inter Core)), asmeasured in Shore C units, preferably has a lower limit of about 30 or32 or 36 or 40 or 45 or 50 or 55 or 60 or 63 or 65 or 67 or 70 or 73 or75 or 76 or 78 Shore C, and an upper limit of about 78 or 80 or 85 or 87or 89 or 90 or 92 or 93 or 95 Shore C. While, the midpoint (or innersurface) hardness of the intermediate core(H_(midpoint of the Inter Core)) preferably is about 25 Shore D orgreater and more preferably is within a range having a lower limit ofabout 26 or 30 or 34 or 36 or 38 or 42 or 48 of 50 or 52 Shore D and anupper limit of about 54 or 56 or 58 or 60 or 62 Shore D. As measured inShore C units, the midpoint hardness of the intermediate core(H_(midpoint of the Inter Core)) preferably has a lower limit of about35 or 38 or 44 or 52 or 58 or 60 or 70 or 74 Shore C and an upper limitof about 76 or 78 or 80 or 84 or 86 or 88 or 90 or 92 or 96 Shore C.

On the other hand, the outer core layer preferably has an outer surfacehardness (H_(outer surface of OC)) of about 40 Shore D or greater, andmore preferably within a range having a lower limit of about 40 or 42 or44 or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or60 or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90Shore D. The outer surface hardness of the outer core layer(H_(outer surface of OC)), as measured in Shore C units, preferably hasa lower limit of about 40 or 42 or 45 or 48 or 50 or 54 or 58 or 60 or63 or 65 or 67 or 70 or 72 or 73 or 76 Shore C, and an upper limit ofabout 78 or 80 or 84 or 87 or 88 or 89 or 90 or 92 or 95 Shore C. And,the inner surface of the outer core layer (H_(inner surface of OC)) ormidpoint hardness of the outer core layer (H_(midpoint of OC)),preferably has a hardness of about 40 Shore D or greater, and morepreferably within a range having a lower limit of about 40 or 42 or 44or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or 60or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90 ShoreD. The inner surface hardness (H_(inner surface of OC)) or midpointhardness (H_(midpoint of OC)) of the outer core layer, as measured inShore C units, preferably has a lower limit of about 40 or 42 or 44 or45 or 47 or 50 or 52 or 54 or 55 or 58 or 60 or 63 or 65 or 67 or 70 or73 or 75 Shore C, and an upper limit of about 78 or 80 or 85 or 88 or 89or 90 or 92 or 95 Shore C.

The midpoint of a core layer is taken at a point equidistant from theinner surface and outer surface of the layer to be measured, mosttypically an outer core layer. Once one or more core layers surround alayer of interest, the exact midpoint may be difficult to determine,therefore, for the purposes of the present invention, the measurement of“midpoint” hardness of a layer is taken within plus or minus 1 mm of themeasured midpoint of the layer.

In one embodiment, the outer surface hardness of the outer core layer(H_(outer surface of OC)), is less than the outer surface hardness(H_(inner core surface)) or midpoint hardness (H_(midpoint of OC)), ofthe inner core by at least 3 Shore C units and more preferably by atleast 5 Shore C.

In a second embodiment, the outer surface hardness of the outer corelayer (H_(outer surface of OC)), is greater than the outer surfacehardness (H_(inner core surface)) or midpoint hardness(H_(midpoint of OC)), of the inner core by at least 3 Shore C units andmore preferably by at least 5 Shore C.

As discussed above, the inner core is preferably formed from athermoplastic composition and more preferably an ethylene acidcopolymer/plasticizer composition. And, the outer core layer is formedpreferably from a thermoset composition such as polybutadiene rubber. Inother embodiments, the outer core layer also may be formed fromthermoplastic compositions, particularly ethylene acidcopolymer/plasticizer compositions.

The core structure also has a hardness gradient across the entire coreassembly. In one embodiment, the (H_(inner core center)) is in the rangeof about 10 Shore C to about 60 Shore C, preferably about 13 Shore C toabout 55 Shore C; and the (H_(outer surface of OC)) is in the range ofabout 65 to about 96 Shore C, preferably about 68 Shore C to about 94Shore C or about 75 Shore C to about 93 Shore C, to provide a positivehardness gradient across the core assembly. In another embodiment, thereis a zero or negative hardness gradient across the core assembly. Forexample, the center of the core (H_(inner core center)) may have ahardness gradient in the range of 20 to 90 Shore C; and the outersurface of the outer core may have a hardness gradient in the range of10 to 80 Shore C. The hardness gradient across the core assembly willvary based on several factors including, but not limited to, thedimensions of the inner core, intermediate core, and outer core layers.

The USGA has established a maximum weight of 45.93 g (1.62 ounces) forgolf balls. For play outside of USGA rules, the golf balls can beheavier. In one preferred embodiment, the weight of the multi-layeredcore is in the range of about 28 to about 38 grams. Also, golf ballsmade in accordance with this invention can be of any size, although theUSGA requires that golf balls used in competition have a diameter of atleast 1.68 inches. For play outside of United States Golf Association(USGA) rules, the golf balls can be of a smaller size. Normally, golfballs are manufactured in accordance with USGA requirements and have adiameter in the range of about 1.68 to about 1.80 inches. As discussedabove, the golf ball contains a cover which may be multi-layered and inaddition may contain intermediate layers, and the thickness levels ofthese layers also must be considered. Thus, in general, the dual-layercore structure normally has an overall diameter within a range having alower limit of about 1.00 or 1.20 or 1.30 or 1.40 inches and an upperlimit of about 1.58 or 1.60 or 1.62 or 1.66 inches, and more preferablyin the range of about 1.3 to 1.65 inches. In one embodiment, thediameter of the core assembly is in the range of about 1.45 to about1.62 inches.

The hardness of the core assembly (for example, inner core, intermediatecore layer, and outer core layer) is an important property. In general,cores with relatively high hardness values have higher compression andtend to have good durability and resiliency. However, some highcompression balls are stiff and this may have a detrimental effect onshot control and placement. Thus, the optimum balance of hardness in thecore assembly needs to be attained. The present invention provides coreassemblies having both good resiliency (CoR) and compression propertiesas demonstrated in the Examples below.

Manufacturing of Golf Balls

The inner core may be formed by any suitable technique includingcompression and injection molding methods. The outer core layer, whichsurrounds the inner core, is formed by molding compositions over theinner core. Compression or injection molding techniques may be used toform the other layers of the core assembly. Then, the cover layers areapplied over the core assembly. Prior to this step, the core structuremay be surface-treated to increase the adhesion between its outersurface and the next layer that will be applied over the core. Suchsurface-treatment may include mechanically or chemically-abrading theouter surface of the core. For example, the core may be subjected tocorona-discharge, plasma-treatment, silane-dipping, or other treatmentmethods known to those in the art.

The cover layers are formed over the core or ball assembly (the corestructure and any intermediate layers disposed about the core) using asuitable technique such as, for example, compression-molding,flip-molding, injection-molding, retractable pin injection-molding,reaction injection-molding (RIM), liquid injection-molding, casting,spraying, powder-coating, vacuum-forming, flow-coating, dipping,spin-coating, and the like. Preferably, each cover layer is separatelyformed over the ball sub-assembly. For example, an ethylene acidcopolymer ionomer composition may be injection-molded to producehalf-shells. Alternatively, the ionomer composition can be placed into acompression mold and molded under sufficient pressure, temperature, andtime to produce the hemispherical shells. The smooth-surfacedhemispherical shells are then placed around the core sub-assembly in acompression mold. Under sufficient heating and pressure, the shells fusetogether to form an inner cover layer that surrounds the sub-assembly.In another method, the ionomer composition is injection-molded directlyonto the core sub-assembly using retractable pin injection molding. Anouter cover layer comprising a polyurethane or polyurea composition overthe ball sub-assembly may be formed by using a casting process.

After the golf balls have been removed from the mold, they may besubjected to finishing steps such as flash-trimming, surface-treatment,marking, coating, and the like using techniques known in the art. Forexample, in traditional white-colored golf balls, the white-pigmentedcover may be surface-treated using a suitable method such as, forexample, corona, plasma, or ultraviolet (UV) light-treatment. Then,indicia such as trademarks, symbols, logos, letters, and the like may beprinted on the ball's cover using pad-printing, ink-jet printing,dye-sublimation, or other suitable printing methods. Clear surfacecoatings (for example, primer and top-coats), which may contain afluorescent whitening agent, are applied to the cover. The resultinggolf ball has a glossy and durable surface finish.

In another finishing process, the golf balls are painted with one ormore paint coatings. For example, white primer paint may be appliedfirst to the surface of the ball and then a white top-coat of paint maybe applied over the primer. Of course, the golf ball may be painted withother colors, for example, red, blue, orange, and yellow. As notedabove, markings such as trademarks and logos may be applied to thepainted cover of the golf ball. Finally, a clear surface coating may beapplied to the cover to provide a shiny appearance and protect any logosand other markings printed on the ball.

Other Ball Constructions

It should be understood that the golf ball constructions described aboveare for illustrative purposes only, and they are not meant to berestrictive. Other golf ball constructions can be made in accordancewith this invention.

For example, very low compression golf balls comprising at least onecore or cover layer of the plasticized thermoplastic composition may bemade. The golf ball preferably has a compression of less than 60, morepreferably less than 50 and may be within a range of from about negative60 to positive 55 DCM. More preferably, the DCM range is from aboutnegative 20 to positive 40, and may be from about zero to 35, and may beabout 5, 10, 20 or 25, 30, 45 or 50 DCM. The ball can be a one-pieceball comprising a single layer of the plasticized thermoplasticcomposition, or a two or more piece ball with one or more layerscomprising the plasticized thermoplastic composition (for example, corelayer, cover layer, and/or intermediate layer). For example, a very lowcompression two-piece ball may comprise either a core of a plasticizedthermoplastic composition, and a cover of ionomer or polyurethane, oralternatively comprises a core of a thermoset polybutadiene and a coverof a plasticized thermoplastic composition. A very low compression threeor more layer ball may comprise a inner core of a plasticizedthermoplastic composition, an outer core of a thermoset polybutadiene,and a cover of an ionomer or polyurethane. A very low compressionfour-layer golf ball be constructed with an inner core layer and anouter core layer, both comprising a thermoset polybutadiene, an innercover layer comprising a plasticized thermoplastic composition, and anouter cover layer comprising an ionomer or polyurethane.

Test Methods

Hardness. The center hardness of a core is obtained according to thefollowing procedure. The core is gently pressed into a hemisphericalholder having an internal diameter approximately slightly smaller thanthe diameter of the core, such that the core is held in place in thehemispherical portion of the holder while concurrently leaving thegeometric central plane of the core exposed. The core is secured in theholder by friction, such that it will not move during the cutting andgrinding steps, but the friction is not so excessive that distortion ofthe natural shape of the core would result. The core is secured suchthat the parting line of the core is roughly parallel to the top of theholder. The diameter of the core is measured 90 degrees to thisorientation prior to securing. A measurement is also made from thebottom of the holder to the top of the core to provide a reference pointfor future calculations. A rough cut is made slightly above the exposedgeometric center of the core using a band saw or other appropriatecutting tool, making sure that the core does not move in the holderduring this step. The remainder of the core, still in the holder, issecured to the base plate of a surface grinding machine. The exposed‘rough’ surface is ground to a smooth, flat surface, revealing thegeometric center of the core, which can be verified by measuring theheight from the bottom of the holder to the exposed surface of the core,making sure that exactly half of the original height of the core, asmeasured above, has been removed to within 0.004 inches. Leaving thecore in the holder, the center of the core is found with a center squareand carefully marked and the hardness is measured at the center markaccording to ASTM D-2240. Additional hardness measurements at anydistance from the center of the core can then be made by drawing a lineradially outward from the center mark, and measuring the hardness at anygiven distance along the line, typically in 2 mm increments from thecenter. The hardness at a particular distance from the center should bemeasured along at least two, preferably four, radial arms located 180°apart, or 90° apart, respectively, and then averaged. All hardnessmeasurements performed on a plane passing through the geometric centerare performed while the core is still in the holder and without havingdisturbed its orientation, such that the test surface is constantlyparallel to the bottom of the holder, and thus also parallel to theproperly aligned foot of the durometer.

The outer surface hardness of a golf ball layer is measured on theactual outer surface of the layer and is obtained from the average of anumber of measurements taken from opposing hemispheres, taking care toavoid making measurements on the parting line of the core or on surfacedefects, such as holes or protrusions. Hardness measurements are madepursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic byMeans of a Durometer.” Because of the curved surface, care must be takento ensure that the golf ball or golf ball sub-assembly is centered underthe durometer indenter before a surface hardness reading is obtained. Acalibrated, digital durometer, capable of reading to 0.1 hardness unitsis used for the hardness measurements and is set to record the maximumhardness reading attained for each measurement. The digital durometermust be attached to, and its foot made parallel to, the base of anautomatic stand. The weight on the durometer and attack rate conforms toASTM D-2240.

In certain embodiments, a point or plurality of points measured alongthe “positive” or “negative” gradients may be above or below a line fitthrough the gradient and its outermost and innermost hardness values. Inan alternative preferred embodiment, the hardest point along aparticular steep “positive” or “negative” gradient may be higher thanthe value at the innermost portion of the inner core (the geometriccenter) or outer core layer (the inner surface)—as long as the outermostpoint (i.e., the outer surface of the inner core) is greater than (for“positive”) or lower than (for “negative”) the innermost point (i.e.,the geometric center of the inner core or the inner surface of the outercore layer), such that the “positive” and “negative” gradients remainintact.

As discussed above, the direction of the hardness gradient of a golfball layer is defined by the difference in hardness measurements takenat the outer and inner surfaces of a particular layer. The centerhardness of an inner core and hardness of the outer surface of an innercore in a single-core ball or outer core layer are readily determinedaccording to the test procedures provided above. The outer surface ofthe inner core layer (or other optional intermediate core layers) in adual-core ball are also readily determined according to the proceduresgiven herein for measuring the outer surface hardness of a golf balllayer, if the measurement is made prior to surrounding the layer with anadditional core layer. Once an additional core layer surrounds a layerof interest, the hardness of the inner and outer surfaces of any inneror intermediate layers can be difficult to determine. Therefore, forpurposes of the present invention, when the hardness of the inner orouter surface of a core layer is needed after the inner layer has beensurrounded with another core layer, the test procedure described abovefor measuring a point located 1 mm from an interface is used. Likewise,the midpoint of a core layer is taken at a point equidistant from theinner surface and outer surface of the layer to be measured, mosttypically an outer core layer. Also, once one or more core layerssurround a layer of interest, the exact midpoint may be difficult todetermine, therefore, for the purposes of the present invention, themeasurement of “midpoint” hardness of a layer is taken within plus orminus 1 mm of the measured midpoint of the layer.

Also, it should be understood that there is a fundamental differencebetween “material hardness” and “hardness as measured directly on a golfball.” For purposes of the present invention, material hardness ismeasured according to ASTM D2240 and generally involves measuring thehardness of a flat “slab” or “button” formed of the material. Surfacehardness as measured directly on a golf ball (or other sphericalsurface) typically results in a different hardness value. The differencein “surface hardness” and “material hardness” values is due to severalfactors including, but not limited to, ball construction (that is, coretype, number of cores and/or cover layers, and the like); ball (orsphere) diameter; and the material composition of adjacent layers. Italso should be understood that the two measurement techniques are notlinearly related and, therefore, one hardness value cannot easily becorrelated to the other. Shore hardness (for example, Shore C or Shore Dhardness) was measured according to the test method ASTM D-2240.

Compression. As disclosed in Jeff Dalton's Compression by Any OtherName, Science and Golf IV, Proceedings of the World Scientific Congressof Golf (Eric Thain ed., Routledge, 2002) (“J. Dalton”), severaldifferent methods can be used to measure compression, including Atticompression, Riehle compression, load/deflection measurements at avariety of fixed loads and offsets, and effective modulus. The DCM is anapparatus that applies a load to a core or ball and measures the numberof inches the core or ball is deflected at measured loads. Aload/deflection curve is generated that is fit to the Atti compressionscale that results in a number being generated that represents an Atticompression. The DCM does this via a load cell attached to the bottom ofa hydraulic cylinder that is triggered pneumatically at a fixed rate(typically about 1.0 ft/s) towards a stationary core. Attached to thecylinder is an LVDT that measures the distance the cylinder travelsduring the testing timeframe. A software-based logarithmic algorithmensures that measurements are not taken until at least five successiveincreases in load are detected during the initial phase of the test.

Coefficient of Restitution (“COR”). The COR is determined according to aknown procedure, wherein a golf ball or golf ball sub-assembly (forexample, a golf ball core) is fired from an air cannon at two givenvelocities and a velocity of 125 ft/s is used for the calculations.Ballistic light screens are located between the air cannon and steelplate at a fixed distance to measure ball velocity. As the ball travelstoward the steel plate, it activates each light screen and the ball'stime period at each light screen is measured. This provides an incomingtransit time period which is inversely proportional to the ball'sincoming velocity. The ball makes impact with the steel plate andrebounds so it passes again through the light screens. As the reboundingball activates each light screen, the ball's time period at each screenis measured. This provides an outgoing transit time period which isinversely proportional to the ball's outgoing velocity. The COR is thencalculated as the ratio of the ball's outgoing transit time period tothe ball's incoming transit time period(COR=V_(out)/V_(in)=T_(in)/T_(out)).

The present invention is illustrated further by the following Examples,but these Examples should not be construed as limiting the scope of theinvention.

The following commercially available materials were used in the belowexamples:

CB23 high-cis neodymium-catalyzed polybutadiene rubber, commerciallyavailable from Lanxess Corporation;

Fusabond® N525 metallocene-catalyzed polyethylene, Fusabond® N416chemically modified ethylene elastomer, Fusabond® C190 anhydridemodified ethylene vinyl acetate copolymer, and Fusabond® P614functionalized polypropylene, commercially available from E. I. du Pontde Nemours and Company;

HPC 1022 is a bimodal ionomer that is 100% neutralized with a zinccation source and the composition of which is described in U.S. Pat.Nos. 6,562,906, and 8,193,283, as well as 8,410,219 and 8,410,220, allof which are incorporated by reference herein;

HPC 1043 is a bimodal ionomer that is 100% neutralized with a magnesiumcation source and the composition of which is described in U.S. Pat.Nos. 6,562,906, and 8,193,283, as well as 8,410,219 and 8,410,220, allof which are incorporated by reference herein;

Nucrel® 9-1, Nucrel® 599, Nucrel® 960, Nucrel® 0407, Nucrel® 0609,Nucrel® 1214, Nucrel® 2906, Nucrel® 2940, Nucrel® 30707, Nucrel® 31001,and Nucrel® AE acid copolymers, commercially available from E. I. duPont de Nemours and Company and particularly

Nucrel® 9-1 is a copolymer of ethylene with 23.5% n-butyl acrylate, andabout 9% methacrylic acid that is unneutralized;

Nucrel® 2940 is a copolymer of ethylene and about 19% methacrylic acidthat is unneutralized;

Nucrel® 0403 is a copolymer of ethylene and about 4% methacrylic acidthat is unneutralized;

Nucrel® 960 is a copolymer of ethylene and about 15% methacrylic acidthat is unneutralized;

Primacor® 3150, 3330, 59801, 5986, and 59901 acid copolymers,commercially available from The Dow Chemical Company—Primacor 5980i and5986 are both copolymers of ethylene with about 20% acrylic acid;

Surlyn® 6320 is based on a copolymer of ethylene with 23.5% n-butylacrylate, and about 9% methacrylic acid that is about 50% neutralizedwith a magnesium cation source, commercially available from E. I. duPont de Nemours and Company;

Surlyn® 8150 is based on a copolymer of ethylene with about 19%methacrylic acid that is about 45% neutralized with a sodium cationsource, commercially available from E. I. du Pont de Nemours andCompany;

Surlyn® 8320 is based on a copolymer of ethylene with 23.5% n-butylacrylate, and about 9% methacrylic acid that is about 52% neutralizedwith a sodium cation source, commercially available from E. I. du Pontde Nemours and Company;

Surlyn® 9120 is based on a copolymer of ethylene with about 19%methacrylic acid that is about 36% neutralized with a zinc cationsource, commercially available from E. I. du Pont de Nemours andCompany; and

Surlyn® 9320 is based on a copolymer of ethylene with 23.5% n-butylacrylate, and about 9% methacrylic acid that is about 41% neutralizedwith a zinc cation source, commercially available from E. I. du Pont deNemours and Company.

Solid spheres of each composition were injection molded, and the solidsphere COR, compression, Shore D hardness, and Shore C hardness of theresulting spheres were measured after two weeks. The results arereported in the Tables below. The surface hardness of a sphere isobtained from the average of a number of measurements taken fromopposing hemispheres, taking care to avoid making measurements on theparting line of the sphere or on surface defects, such as holes orprotrusions. Hardness measurements are made pursuant to ASTM D-2240“Indentation Hardness of Rubber and Plastic by Means of a Durometer.”Because of the curved surface, care must be taken to ensure that thesphere is centered under the durometer indentor before a surfacehardness reading is obtained. A calibrated, digital durometer, capableof reading to 0.1 hardness units is used for all hardness measurementsand is set to record the maximum hardness reading obtained for eachmeasurement. The digital durometer must be attached to, and its footmade parallel to, the base of an automatic stand. The weight on thedurometer and the attack rate conform to ASTM D-2240.

In the following examples, acid copolymer compositions (which containfully neutralized, bimodal ionomers) were made. These compositions andthe properties of these materials are described in Table 1 below. Allpercentages are based on total weight percent of the composition, unlessotherwise indicated.

TABLE 1 Properties of Solid Spheres Made from BimodalIonomer/Plasticizer Compositions. SFI SFI SFI First 2nd CoR@ Shore DShore C Compression Shore D Shore C Ex. Ingr. Ingr. 125 ft/s DCMHardness Hardness (DCM) Hardness Hardness 1A HPC 0.495 43 32.0 54.4−0.299 −0.261 −0.263 AD1022 (100%) 1B HPC Ethyl 0.544 2 24.1 46.0 −0.195−0.157 −0.178 AD1022 Oleate (90%) (10%) 1C HPC 0.687 78 38.9 71.6 −0.153−0.117 −0.146 AD1043 (100%) 1D HPC Ethyl 0.717 49 31.7 62.8 −0.084−0.037 −0.078 AD1043 Oleate (90%) (10%) 1E HPC Ethyl 0.714 19 27.7 45.9−0.048 −0.012 −0.007 AD1043 Oleate (80%) (20%) 1F HPC Ethyl 0.554 −4121.4 31.9 −0.129 −0.128 −0.107 AD1022 Oleate (80%) (20%) 1G HPC Ethyl0.684 −20 21.5 31.5 −0.026 0.002 0.025 AD1043 Oleate (70%) (30%) 1H HPCEthyl 0.526 −89 15.9 20.6 −0.093 −0.117 −0.086 AD1022 Oleate (70%) (30%)

In the following examples, acid copolymer ionomer blend compositionswere made. These compositions and the properties of these materials aredescribed in Table 2 below. All percentages are based on total weightpercent of the composition, unless otherwise indicated.

TABLE 2 Properties of Solid Spheres Made from Acid Copolymer IonomerBlend Compositions. First Second Third Ingre- Ingre- Ingre- CoR@ Shore DShore C Ex. dient dient dient 125 ft/s DCM Hardness Hardness 2A SurlynSurlyn 0.722 151 65.3 92.3 6910 8320 (77%) (23%) 2B Surlyn Surlyn Ethyl0.753 141 59.1 87.5 6910 8320 Oleate (70%) (21%) (9%) 2C Surlyn Surlyn0.708 157 63.6 89.9 7940 8320 (77%) (23%) 2D Surlyn Surlyn Ethyl 0.682144 54.7 82.4 7940 8320 Oleate (70%) (21%) (9%) 2E Surlyn Surlyn 0.683157 62.9 89.7 8945 8320 (77%) (23%) 2F Surlyn Surlyn Ethyl 0.651 14052.0 78.6 8945 8320 Oleate (70%) (21%) (9%) 2G Surlyn Surlyn 0.645 15460.1 87.1 9945 8320 (77%) (23%) 2H Surlyn Surlyn Ethyl 0.627 131 50.476.0 9945 8320 Oleate (70%) (21%) (9%)

As shown in above Table 2, sample ethylene acid copolymer ionomer andethylene acid ester terpolymer ionomer blends were prepared, and sphereswere made from these blend compositions. Some of the ionomer blends didnot contain plasticizer (Samples 2A, 2C, 2E, and 2G), while otherionomer blends contained plasticizer (Samples 2B, 2D, 2F, and 2H).Interestingly, only Sample 2B showed an increase in CoR versus itsrespective control (Sample 2A). In this instance, it is believed thecomposition of the ionomer blend is significant. The ionomer blendcontaining plasticizer in Sample 2B used a blend of Mg/Na cations as theneutralizing agent for the acid groups. In contrast, the other ionomerblends containing plasticizer in Table 2 used a blend of Li/Na cations(Sample 2D), or a blend of Na/Na cations (Sample 2F), or a blend ofZn/Na cations (Sample 2H) as the neutralizing agent. In one preferredembodiment of this invention, a composition comprising an ethylene acidcopolymer ionomer and ethylene acid ester terpolymer ionomer blendcontaining a blend of Mg/Na cations is used to form the outer or innercover layer or other layer of the golf ball construction.

In the following examples, some sample highly neutralized (HNP) ethyleneacid copolymer compositions were made and the hardness values (Shore Cand Shore D) of these materials were measured. These compositions andthe properties of these materials are described in Tables 3 and 3Abelow. All percentages are based on total weight percent of thecomposition, unless otherwise indicated.

The hardness of the sample spheres was measured at their outer surfaceand geometric centers. The hardness gradient is determined bysubtracting the hardness value at the geometric center of the spherefrom the hardness value at the outer surface of the sphere. If thehardness value of the outer surface is greater than the hardness valueof the center, the hardness gradient is deemed “positive.” Conversely,if the hardness value of the outer surface of the sphere is less thanthe hardness value of the sphere's center, the hardness gradient will be“negative.” As reported in below Tables 3 and 3A, the samplesdemonstrate a wide range of “surface-to-center” gradients includingpositive, negative, and zero hardness gradients.

For the below Samples in Tables 3 and 3A, and for all plasticizedthermoplastic compositions herein, it is generally established that thehardness measured at any point in between the geometric and the outersurface is within plus or minus 7, and more preferably within plus orminus 5, and most preferably within plus or minus 3 of the geometriccenter hardness and the surface hardness values. That is, for Sample“3A”, the hardness at any point between the geometric center and theouter surface is most preferably, within a range of from 77.1 to 95.9Shore C, and typically is a value that is between the geometric centerand the outer surface, i.e., is within the range of from 80.1 Shore C to92.9 Shore C. Therefore, the hardness at any point between the geometricand the outer surface of Sample “3A” may, most preferably, be a value of78, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, or 95 ShoreC.

Likewise for above Sample “3F”, the hardness measured at any pointbetween the geometric center and the outer surface will, mostpreferably, be within a range of from 32.5 to 44.4, and for Sample “3D”,the hardness measured at any point between the geometric center and theouter surface will, most preferably, be within a range of from 63.5 to71.5 Shore C, and so forth for other plasticized thermoplasticcompositions

TABLE 3 Hardness Gradients of Sample HNP/Plasticizer Compositions FirstSecond Aging of Sphere Example Ingredient Ingredient (Weeks) 3A HPF 100020 (100%) 3B HPF 1000 Ethyl Oleate 21 (90%) (10%) 3C HPF 2000 20 (100%)3D HPF 2000 Ethyl Oleate 20 (90%) (10%) 3E HPF 2000 Ethyl Oleate 9 (80%)(20%) 3F HPF 1000 Ethyl Oleate 9 (70%) (30%)

TABLE 3A Hardness Gradient of Sample HNP/Plasticizer Compositions SphereSphere Surface- Sphere Sphere Surface- Surface Center to-Center SurfaceCenter to-Center Hardness Hardness Gradient Hardness Hardness GradientExample (Shore C) (Shore C) (Shore C) (Shore D) (Shore D) (Shore D) 3A92.9 80.1 12.8 58.6 50.5 8.1 3B 85.4 74.2 11.2 54.0 43.8 10.2 3C 78.575.1 3.4 47.4 45.8 1.6 3D 68.5 66.5 2.0 38.4 37.6 0.8 3E 51.8 53.4 −1.629.4 27.7 1.7 3F 35.5 41.4 −5.9 20.3 21.7 −1.4

The melt flow index of the compositions also can be measured using ASTMD-1238 at 190° C. with a 2160 gram weight. In a preferred embodiment,the addition of the plasticizer increases the melt flow index of thecomposition by a magnitude of at least 0.5 g/10 minutes, more preferablyat least 1.0 g/10 minutes, and even more preferably at least 2.0 or 3.0g/10 minutes.

In the following Prophetic Examples, different golf ball constructionsare prepared and the properties of these balls are reported. To preparethese sample balls, different core formulations (see below Table 5) areprepared and these formulations are molded into spherical core layers.Then, different cover formulations (see below Tables 4 and 4A) areprepared and these formulations are molded into covers overlying thecore layers. The properties of the resulting balls are reported in belowTable 6.

TABLE 4 Cover Layer Formulations Sample No. E1 E2 E3 E4 E5 E6 E7 E8 CE1Composition HPF 2000 80 100 HPF 1000 90 HPC AD1022 90 HPC AD1043 90 85.7Primacor 5980i 16.5 Surlyn 6320 90 Nucrel 2940 90 Fusabond N525 34.2Oelic Acid 33.9 Magnesium Hydroxide 5.4 Ethyl Oleate 20 10 10 10 10 109.5 10 White MB 4.8 Properties Compression 32 31 59 38 2 49 52 99 91Shore C 53.0 60.2 58.4 56.8 46.0 62.8 64 81.2 76.5 Shore D 30.2 34.336.7 29.4 24.1 31.7 33 47.2 46.1 CoR at 125 ft/s 0.810 0.783 0.458 0.6990.544 0.717 0.714 0.846 0.856

TABLE 4A Additional Cover Layer Formulations Sample No. CE2 CE3 CE4 CE5CE6 CE7 CE8 CE9 CE 10 Composition HPC AD1022 100 HPC AD1043 100 Surlyn6320 100 Primacor 5980i 18.3 Nucrel 2940 100 Fusabond N525 38.1 14.2Oleic acid 37.6 Magnesium Hydroxide 6 Ethyl Oleate Surlyn 8940 50 42.947.6 Surlyn 7940 38.1 50 38.1 47.6 White MB 37.6 4.8 4.8 6.5% NCOMDI/PTMEG 6.0 83.4 Prepolymer Ethacure 300 Curative 16.6 blend with TiO2Properties Compression 135 141 81 43 78 158 150 128 157 Shore C 90.284.2 71.3 54.4 71.6 95 92 72 95 Shore D 61.5 54.3 41.9 32.0 38.9 67 6450 67 CoR at 125 ft/s 0.873 0.594 0.666 0.495 0.687 0.744 0.730 0.6520.744

TABLE 5 Core Formulations Sample No. a b c d Composition (phr) (phr)(phr) (phr) Polybutadiene 100 100 0 100 Zinc diacrylate 18 27 0 27Process Aid 1 1 0 1 Antioxidant 0 0.25 0 0.5 Peroxide 0.6 1 0 0 Zn PCTP0.5 0.5 0 0 Zinc oxide 12 12 0 13 Polywate 324 26.5 27 20 27 Tungstenpowder 0 0 26 0 E8*¹ 0 0 100 100 *¹Example as found in above Table 4

TABLE 6 Sample Ball Properties Sample No. 8-1 8-2 8-3 8-4 Composition aE1 None None Inner Core Properties Size 0.8 1.1″ — — Atti Compression 1833 — — CoR 0.761 0.805 — — Shore C Surface (H_(inner core surface)) 5753 — — Shore C Center (H_(inner core center)) 48 49 — — Outer CoreProperties Composition b c b d Size 1.45″ 1.53″ 1.40″ 1.40″ AttiCompression 45 83 65 56 CoR 0.778 0.806 0.785 0.774 Shore C Surface(H_(outer surface of oc)) 76 85 80 78 Shore C Midpoint(H_(midpoint of OC)) 55 82 57 63 Core Gradient 28 36 23 15 Inner CoverLayer Composition E1 CE7 E2 CE1 Size 1.57″ 1.610″ 1.54″ 1.54″ Shore DSurface (H_(surface of Inner cov)) 53C 69D 35D 47D Shore D Midpoint 51C68D 34D 46D (H_(midpoint of Inner Cov)) Atti Compression 46 96 64 61 CoR0.773 0.815 0.784 0.795 Intermediate Cover Layer Composition None NoneCE7 E4 Size — — 1.62″ 1.61″ Shore D Surface — — 69D 31D(H_(surface of Intermed cov)) Shore D Midpoint — — 68D 30D(H_(midpoint of Intermed covC)) Atti Compression — — 89 60 CoR — — 0.8140.785 Outer Cover Layer Composition CE8 E7 CE9 CE10 Ball PropertiesShore D Surface Hardness 66D 53D 63D 69D Atti Compression 69 97 91 76CoR 0.804 0.812 0.802 0.811 Initial velocity 253.9 254 252.8 254.6

It is understood that the compositions and golf ball products describedand illustrated herein represent only some embodiments of the invention.It is appreciated by those skilled in the art that various changes andadditions can be made to compositions and products without departingfrom the spirit and scope of this invention. It is intended that allsuch embodiments be covered by the appended claims.

We claim:
 1. A golf ball, comprising; i) a core having at least onelayer; ii) an inner cover layer comprising a thermoplastic material, theinner cover layer being disposed about the core and having a Shore Dmidpoint hardness in the range of about 15 to about 60, thethermoplastic material comprising: a) an acid copolymer of ethylene andan α,β-unsaturated carboxylic acid, optionally including a softeningmonomer selected from the group consisting of alkyl acrylates andmethacrylates; b) an alkyl oleate plasticizer selected from the groupconsisting of methyl oleate, ethyl oleate, propyl oleate, butyl oleate,and octyl oleate, and mixtures thereof; and c) a cation source presentin an amount sufficient to, neutralize from about 0 to about 100% of allacid groups present in the material; and iii) an outer cover layerdisposed about the inner cover layer and having a Shore D surfacehardness in the range of about 55 to about 75, wherein the hardness ofthe outer cover layer is greater than the hardness of the inner coverlayer.
 2. The golf ball of claim 1, wherein the thermoplastic materialcomprises about 3 to about 50% by weight plasticizer.
 3. The golf ballof claim 1, wherein the thermoplastic material comprises an ethyleneacid copolymer containing acid groups such that 70% of the acid groupsare neutralized.
 4. The golf ball of claim 1, wherein the thermoplasticmaterial comprises an ethylene acid copolymer containing acid groupssuch that greater than 70% of the add groups are neutralized.
 5. Thegolf ball of claim 4, wherein 90% or greater of the acid groups areneutralized.
 6. The golf ball of claim 1 wherein the ethylene acidcopolymer is selected from the group consisting ofethylene/(meth)acrylic acid/n-butyl acrylate; ethylene/(meth)acrylicacid/ethyl acrylate; ethylene/(meth)acrylic acid/methyl acrylate;ethylene/(meth)acrylic acid/n-butyl acrylate; and ethylene/(meth)acrylicacid/isobutyl acrylate copolymers.
 7. The golf ball of claim 1, whereinthe inner cover layer has a Shore D midpoint hardness in the range ofabout 25 to about 58 and the outer cover layer has a Shore D surfacehardness in the range of about 58 to about 71, wherein the hardness ofthe outer cover layer is greater than the hardness of the inner coverlayer.
 8. The golf ball of claim 1, wherein the core is a core assemblycomprising: i) an inner core layer comprising a thermoplasticcomposition, the inner core having an outer surface hardness(H_(inner core surface)) and a center hardness (H_(inner core center)),the H_(inner core surface) being greater than the H_(inner core center)to provide a positive hardness gradient, ii) an outer core layercomprising a thermoset rubber composition, the outer core layer beingdisposed about the inner core layer and having an outer surface hardness(H_(outer surface of OC)) and a midpoint hardness(H_(midpoint of OC)),the H_(outer surface of OC) being greater than the H_(midpoint of OC) toprovide a positive hardness gradient, wherein the center hardness of theinner core (H_(inner core center)) is in the range of about 10 Shore Cto about 70 Shore C and the outer surface hardness of the outer corelayer (H_(outer surface of OC))is in the range of about 20 Shore C toabout 95 Shore C to provide a positive hardness gradient across the coreassembly.
 9. The golf ball of claim 8, wherein the thermoplasticcomposition comprises a) an acid copolymer of ethylene and anα,β-unsaturated carboxylic acid, optionally including a softeningmonomer selected from the group consisting of alkyl acrylates andmethacrylates; b) a plasticizer; and c) a cation source present in anamount sufficient to neutralize from about 0 to about 100% of all acidgroups present in the composition.
 10. The golf ball of claim 1, whereinthe core is a core assembly comprising: i) an inner core layercomprising a thermoset rubber material, the inner core having an outersurface hardness (H_(inner core surface)) and a center hardness(H_(inner core center)), the H_(inner core surface) being greater thanthe H_(inner core center) to provide a positive hardness gradient; ii)an outer core layer comprising a thermoplastic material, the outer corelayer being disposed about the inner core layer and having an outersurface hardness (H_(outer surface of OC))and a midpoint hardness(H_(midpoint of OC)), the H_(outer surface of OC) being greater than theH_(midpoint of OC) to provide a positive hardness gradient, wherein thecenter hardness of the inner core (H_(inner core center)) is in therange of about 10 Shore C to about 70 Shore C and the outer surfacehardness of the outer core layer (H_(outer surface of OC)) is in therange of about 20 Shore C to about 95 Shore C to provide a positivehardness gradient across the core assembly.
 11. The golf ball of claim10, wherein the thermoplastic material comprises a) an acid copolymer ofethylene and an α,β-unsaturated carboxylic acid, optionally including asoftening monomer selected from the group consisting of alkyl acrylatesand methacrylates; b) a plasticizer; and c) a cation source present inan amount sufficient to neutralize from about 0 to about 100% of allacid groups present, in the composition.